There are at least two ways to solve this.
Solution 1:
If you are okay with using an absolutely positioned element, you can use the top
and bottom
properties instead of height
. By setting both top
and bottom
to 0
you force the element into taking up full height.
#menu
{
position: absolute;
border-right: 1px solid black;
top: 0;
bottom: 0;
}?
Solution 2:
Another way would be to force the HTML and BODY elements into a 100% height, to give room for a menu with 100% height:
body, html { height: 100%; }
#menu
{
border-right: 1px solid black;
height: 100%;
}?