Blix theme, Firefox and IE display problems

Hello,

I hope that there are some Blix fans out there, who could help with advise.
My page is: http://www.bioteka.lv
Theme used – Blix.

At the beginning, page was showing fine in both browsers, then I did some tweaking with sidebar code, and now sidebar is down below the posts. however, shows fine in Firefox.

I can’t figure out, what is wrong, maybe somebody can look at it and give some hint?
Funny fact is that before the twaking I made a backup of all major files (layout.css, index, sidebar etc.). When problem appreared, I reverted back to working backup files, but problem is stull there! Cleared cache in all browsers, no result…

Thank you!