(I have set a height 100% in my body)
I have 1 large 'container' div holding 3 columns.
The center column holds content and the 2 flanking columns are navigation.
Both flanking columns have a background image.
I need the 2 flanking (navigation) columns to ALWAYS be the same height as the content column.
Div Heights!!!! Argghhhh!
However there is a CSS method that relies on using the side borders of a div to give the effect of a full size column.
The borders are set to the size of the required column.(e.g. border:150px solid #fff;) and then the column content is floated in the border using a negative offset from the parent div. As the borders are part of the div they will always expand with the content. (In truth its a little more complicated than that.)
This technique is I believe the only way to achieve the appearance of the three column layout where each column stays the same size. Here is a link to the layout and its author Doug Livingstone.
I hope you find it useful and informative.