I have three divs: header, left and right, and I am using border-right to add a line separating the two divs. The problem that I am having is that the border only spans the length of the content and not the entire page. How can I make the border extend to fill the entire page?

.leftdiv{
width:36.5%;
border-right:1px solid #222222;
float:left;
}
The problem is that the div will only grow to be as large as the content inside of it needs it to be. The border is just a visual cue to that.
You could throw a min-height on the div to make it extend as far as you want it.
The other solution would be to create faux columns, but your best bet may be in this article:
http://css-tricks.com/fluid-width-equal-height-columns/