Wierd Border issue with IE

[dalar]

Hi everyone.

I've got a problem, basically I have a calendar generated via javascript, and has its own CSS style.

Today's date contains a 2px border around its cell, when hovering over any cell, the background should be light grey - this works well across all browsers.

When hovering over today's date, the background turns grey just like it and every cell should, along with this the border around todays date should also dissapear - this works too, however in IE it nudges everything around.

Ive searched the net for answers, I thought it was IE6's dreaded content box problem, but this is also happening in IE7!

In FF and other non-IE browsers its fine.

Any ideas?

* please see attached

attached within zip are:

+ html file
+ 1 js file for menu
+ 1 css file for menu
+2 images


Thank you for your help in advance!