Extended Backgrounds
Extended backgrounds are actually very easy to make in Paint. Just follow this tutorial and you'll see what I mean:)
Step 1: Firstly, open your MS Paint program, then click Image >> Attributes. Since an extended background has to be quite long, make the size 2000x70 pixels.
Step 2: Fill it with the color you want to have as the background. I've choosen a light grey color.
Step 3: Select the
rectangle tool, which looks like this:

. Make one or two rectangles, like I've done:
Step 4: The extended background can be finished now, but if you want you can add some more rectangles to make it a little more interesting;) I've choosen to add some more, here's my finished extended background (click to enlarge):
Step 5: Upload your finished background and paste the URL in this code on the page you want the background: