As most people know,
a 100% div with a 5px padding is actually 100% + 10px wide.
One obvious solution to this is to wrap the child div in a wrapper that has
You should look into the box-sizing
CSS property...
I put together an example to show you how this works and the difference between having the box-sizing
property and not having it. Check out the fiddle...
http://jsfiddle.net/UnsungHero97/bKsad/2/
Note that this won't work in IE7 or below :/
I hope this helps.
Hristo