Lesson 10: Tables

Tables are used when you need to show "tabular data" i.e. information that is logically presented in rows and columns.

Is it difficult?

Building tables in HTML may at first seem complicated but if you keep cool and watch your step, it is actually strictly logical - just like everything else in HTML.

Example 1:

        <table>

          <tr>

               <td>Cell 1</td>

               <td>Cell 2</td>

          </tr>

          <tr>

               <td>Cell 3</td>

               <td>Cell 4</td>

          </tr>

        </table>

Will look like this in the browser:

Cell 1	Cell 2
Cell 3	Cell 4

What's the difference between <tr> and <td>?

As you will see from the above example, this is probably the most complicated HTML example we have given you so far. Let's break it down and explain the different tags:

3 different elements are used to insert tables:

• The opening tag <table> and the closing tag </table> starts and ends the table. Logical.
• <tr> stands for "table row" and starts and ends horizontal rows. Still logical.
• <td> is short for "table data". This tag starts and ends each cell in the rows of your table. All simple and logical.

Here is what happens in Example 1: the table starts with a <table>, followed by a <tr>, which indicates the beginning of a new row. Two cells are inserted in this row: <td>Cell 1</td> and<td>Cell 2</td>. The row is hereafter closed with a </tr> and a new row <tr> begins immediately after. The new row also contains two cells. The table is closed with </table>.

Just to make it clear: rows are horizontal lines of cells and columns are vertical lines of cells:

Cell 1	Cell 2
Cell 3	Cell 4

Cell 1 and Cell 2 form a row. Cell 1 and Cell 3 form a column.

In the above example, the table has two rows and two columns. However, a table can have an unlimited number of rows and columns.

Example 2:

        <table>

          <tr>

               <td>Cell 1</td>

               <td>Cell 2</td>

               <td>Cell 3</td>

               <td>Cell 4</td>

          </tr>

          <tr>

               <td>Cell 5</td>

               <td>Cell 6</td>

               <td>Cell 7</td>

               <td>Cell 8</td>

          </tr>

          <tr>

               <td>Cell 9</td>

               <td>Cell 10</td>

               <td>Cell 11</td>

               <td>Cell 12</td>

          </tr>

        </table>

Will look like this in the browser:

Cell 1	Cell 2	Cell 3	Cell 4
Cell 5	Cell 6	Cell 7	Cell 8
Cell 9	Cell 10	Cell 11	Cell 12

Are there any attributes?

Of course there are attributes. For example, the border attribute is used to specify the thickness of the border around your table:

Example 3:

        <table border="1">

          <tr>

               <td>Cell 1</td>

               <td>Cell 2</td>

          </tr>

          <tr>

               <td>Cell 3</td>

               <td>Cell 4</td>

          </tr>

        </table>

Will look like this in the browser:

Cell 1	Cell 2
Cell 3	Cell 4

The thickness of the border is specified in pixels (See lesson 9)

As with images, you can also set the width of a table in pixels - or alternatively in percentage of the screen:

Example 4:

        <table border="1" width="30%">

This example will be displayed in the browser as a table with the width of 30% of the screen. Try it yourself.

More attributes?

There are lots of attributes for tables. Here are two more:

• align: specifies the horizontal alignment of the content in the entire table, in a row or in a single cell. For example, left, center or right.
• valign: specifies the vertical alignment of the content in a cell. For example, top, middle or bottom.

Example 5:

        <td align="right" valign="top">Cell 1</td>

What can I insert in my tables?

Theoretically, you can insert anything in tables: text, links and images... BUT tables are meant for presenting tabular data (i.e. data which can be meaningfully presented in columns and rows) so refrain from putting things into tables simply because you want them to be placed next to each other.

In the old days on the Internet - i.e. a few years ago - tables were often used as a layout tool. But if you want to control the presentation of texts and images there is a much cooler way to do it (hint: CSS). But more about that later.

Now, put what you just learned to practice and design a number of tables in different sizes, with different attributes and content. This should keep you busy for hours.

Lesson 9: Images

Wouldn't it be great if you could have an image of actor and music legend David Hasselhoff right in the centre of your page?

That sounds like a bit of a challenge...

Maybe, but in fact it is pretty easy to do. All you need is an element:

Example 1:

        <img src="david.jpg" alt="David" />

would look like this in the browser:

All you need do is first tell the browser that you want to insert an image (img) and then where it is located (src, short for "source"). Do you get the picture?

Notice how the img element is opened and closed using the same tag. Like the <br /> tag, it is not tied to a piece of text.

"david.jpg" is the name of the image file you want to insert in your page. ".jpg" is the file type of the image. Just like the extension ".htm" shows that a file is an HTML document, ".jpg" tells the browser that a file is a picture. There are three different types of image file types you can insert into your pages:

• GIF (Graphics Interchange Format)
• JPG / JPEG (Joint Photographic Experts Group)
• PNG (Portable Network Graphics)

GIF images are usually best for graphics and drawings, while JPEG images are usually better for photographs. This is for two reasons: first, GIF images only consist of 256 colours, while JPEG images comprise of millions of colours and second, the GIF format is better at compressing simple images, than the JPEG format which is optimized for more complex images. The better the compression, the smaller the size of the image file, the faster your page will load. As you probably know from your own experience, unnecessarily 'heavy' pages can be extremely annoying for the user.

Traditionally, the GIF and JPEG formats have been the two dominant image types, but lately, the PNG format has become more and more popular (primarily at the expense of the GIF format). The PNG format contains in many ways the best of both the JPEG and GIF format: millions of colours and effective compressing.

Where do I get my images from?

To make your own images, you need an image editing program. An image editing program is one of the most essential tools you need to create beautiful websites.

Unfortunately, no good image editing programs comes with Windows or other operating systems. Thus, you might consider investing in either Paint Shop Pro,PhotoShop or Macromedia Fireworks, which are three of the best image editing programs currently on the market.

However, as we said before, it will not be necessary to buy expensive programs to complete this tutorial. For now, you can download the excellent image editing program IrfanView

 which is so-called freeware and therefore costs nothing.

Or you can just borrow images from other sites by downloading them. But please be careful not to violate copyrights when downloading pictures. Still, it's useful to know how to download pictures, so here's how you do it:

1. Right-click on an image on any image on the Internet.
2. Choose "Save picture as..." in the menu that appears.
3. Choose a location for the image on your computer and press "Save".

Do this with the image below and save it on your computer at the same location as your HTML documents. (Notice that the logo is saved as a PNG file: logo.png):

Now you can insert the image into one of your own pages. Try it yourself.

Is that all I need to know about images?

There are a few more things you should know about images.

First, you can easily insert pictures located in other folders, or even pictures that are located on other websites:

Example 2:

        <img src="images/logo.png" />

Example 3:

        <img src="http://www.html.net/logo.png" />

Second, images can be links:

Example 4:

        <a href="http://www.html.net">

        <img src="logo.png" /></a>

will look like this in the browser (try clicking on the image):

Are there any other attributes I should know about?

You always need to use the attribute src, which tells the browser where the image is located. Besides that, there are a number of other attributes which can be useful when inserting images.

The alt attribute is used to give an alternate description of an image if, for some reason, the image is not shown for the user. This is especially important for users with impaired vision, or if the page is loaded very slowly. Therefore, always use the alt attribute:

Example 5:

        <img src="logo.gif" alt="HTML.net logo" />

Some browsers let the text of the alt attribute appear as a small pop-up box when the user places their cursor over the picture. Please note that when using the alt attribute, the aim is to provide an alternative description of the picture. The alt attribute should not be used to create special pop-up messages for the user since then visually impaired users will hear the message without knowing what the picture is.

The title attribute can be used to add information to the image:

Example 6:

        <img src="logo.gif" title="Learn HTML from HTML.net" />

Will look like this in the browser:

If you, without clicking, place the cursor over the image, you will see the text "Learn HTML from HTML.net" appear as a pop-up box.

Two other important attributes are width and height:

Example 7:

        <img src="logo.png" width="141px" height="32px" />

will look like this in the browser:

The width and height attributes can be used to set the height and width of an image. The value that is used to set the width and height is pixels. Pixels are the units of measurement used to measure the resolution of screens. (The most common screen resolution is 1024x768 pixels). Unlike centimetres, pixels are relative units of measurement which depend on the resolution of the screen. To a user with a high screen resolution, 25 pixels may correspond to 1centimetre, while the same 25 pixel in a low screen resolution may correspond to 1.5 centimetres on the screen.

If you do not set the width and height, the image will be inserted in its actual size. But with width and height you can manipulate the size:

Example 8:

        <img src="logo.gif" width="32px" height="32px" />

will look like this in the browser:

However, it is worth keeping in mind that the actual size in kilobytes of the image file will remain the same so it will take the same time to load the image as it did before, even though it appears smaller on the screen. Therefore, you should never decrease the image size by using the width and height attributes. Instead, you should always resize your images in an image editing program to make your pages lighter and faster.

That said, it is still a good idea to use the width and height attributes because the browser will then be able to detect how much space the image will need in the final page layout before the image is fully downloaded. This allows your browser to set up the page nicely in a quicker way.

That's enough about David Hasselhoff and images for now.

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How to set up WPA2 on your wireless network

If you are like most people, your home or small office wireless router probably is running without any encryption whatsoever, and you are a sitting duck for someone to easily view your network traffic.

Some of you have put encryption on your wireless networks but aren't using the best wireless security methods. This means that you are running your networks with inferior protocols that offer a false sense of protection because these protocols are very easily broken into. It is the difference between using a deadbolt and a simple lock on your front door. For instance, Tom's Networking has a three-part series that shows you how easy it is to crack Wired Equivalent Privacy.

If you want to keep your neighbors out of your business, then you need to use Wi-Fi Protected Access version 2 (WPA2) encryption. This is now showing up on a number of routers and is worth the extra few steps involved to make sure your communications are secure. It is currently the best encryption method but getting it going isn't so simple. This recipe will show you how to make it work.

How does WPA2 differ from earlier versions? First, it supports the 802.11i encryption standards that have been ratified by the IEEE. These are the commercial-grade encryption products that are available on enterprise-class products.

Second, there are two encryption methods that WPA2 adds: one called Advanced Encryption Standard (AES) and one called Temporal Key Integrity Protocol (TKIP). Both of these allow for stronger encryption, and while the differences between the two aren't that important for our purposes, you should pick one method when you set up your network as you'll see in a moment.

Finally, the protocol creates a new encryption key for each session, while the older encryption standards used the same key for everybody -- which is why they were a lot easier to crack.

Also part of the new standard is Pairwise Master Key caching, where faster connections occur when a client goes back to a wireless access point to which the client already is authenticated. There is one more acronym I'll mention, and that is Pre-Shared Key or PSK. The WPA2 standard supports two different authentication mechanisms: one using standard RADIUS servers and the other with a shared key, similar to how WEP works. We'll get back to this in a moment, but let's show you how to get this train going.

Step 1: Windows OS: First make sure your operating system is up to date. If you are running Windows XP, you'll need service pack 2 and you'll need to download the WPA2 patch that's located here.

If you're using a Mac, you need to be running OS X 10.4.2 or better. Apple calls its version WPA2 Personal. While Linux is outside the scope of this article, you can get more information here.

Step 2: Wireless Adapter: While you are updating your Windows OS, you might want to make sure that the wireless adapter in your laptop is also up to the task of supporting WPA2. The Wi-Fi Alliance maintains an online database of products that is somewhat difficult to use. Go to their Web site, check the WPA2 box and then select which vendor you are interested in.

If you have a built-in Intel wireless adapter, it needs to be running Intel's ProSet version 7.1.4 or better, excluding versions 8.x. You can get more information on this page on Intel's Web site.

Step 3: Wireless access point/router: Next, make sure your router/gateway can support WPA2. If you have purchased it in the last year, chances are good that it does, but you might need to update your firmware as well. For the Belkin Pre-N router model 2000, I needed to update the firmware to version 2.01. An older model 1000 didn't support WPA2 and couldn't be upgraded. How can you tell the difference when you are buying one? You can't, other than opening the box and looking at the label on the bottom of the unit.

Here is how you set up the wireless security section of your router to support WPA2. In our examples here, we chose WPA2-AES. Here's a screenshot for the Belkin router:

You'll notice that you can obscure the key from being shown on the screen, which is a nice feature. That is the PSK that we mentioned earlier. Keep track of this; you'll need it later.

With this recipe, I also tried a Netgear WNR854T router, which didn't need any firmware update to support WPA2. Here is the screenshot from the Netgear router, where you can see the shared passphrase on the screen in the clear:

If you are using Apple's Airport router, you need to download the patch for Airport 4.2 here.

Step 4. Finishing the configuration: Now comes the fun part. Once you have your routers set up, you need to get the clients working properly. I'll show you the screens for Windows, but the Mac is similar.

The biggest issue is that you have to remember the PSK that you used to set up the router and enter it when prompted by the OS. You can enter any phrase from 8 to 63 characters, and obviously the longer the better. Don't forget to match the right combination of acronyms that you chose when you set up your router to match what is required in Windows' Wireless Properties Association dialog box, as shown in this screenshot:

Do this for all of the client computers on your network. Once you get everything working, if you take a look at your wireless connections screen, you should see something like this, where the wireless3 access point is showing that it has WPA2 security enabled:

OK, now you should be done. If you aren't getting a connection, chances are there is a mismatch between your router and your client. Check all the steps and make sure that the WPA2 choices are showing up in the right places and that you have chosen the appropriate encryption method (AES or TKIP) for both router and client pairs. You might also have to use the wireless management software from your adapter vendor, rather than Microsoft's, to set up your connection. Once you have a working connection, you don't have to go through all these steps and should be connected securely automatically.