Matching column script not quite working

Hello,

I’ve been using a matching column script for all my sites written in either html or php. For some reason the script doesn’t fully work when used in a wordpress theme. The result is O.K. in explorer, but for Firefox and other browsers the main panel is getting pushed down about 20px below the bottom of the other column.(sidebar)

You can see the result at this url: https://really-valid-info.com/blog/ I’ve added a border to the divs to make it easier to see the result.

Just wondering what other people are using to get matching columns?
If you can recommend a script that works with WordPress or can point me to an alternative method, I’d be grateful.

Many thanks,

Myles