How to debug behaviour in IE6/7 which works completely error-free in other browsers

Question is really simple, I am unable to find out what is wrong with this page:

http://www.ezotour.sk/page/poznavacie-zajazdy-taliansko-sicilia.html

I have tried firebug no errors, I have tried chrome with开发者_运维知识库 no errors, I have tried IE9 with no errors. Using IETester it will return errors in code but I am not able to find out what it is.

I don't want you to debug my page for me, I need some advice what you use for IE6/7 debugging.

IETester is buggy, don't trust it.

The best way to test across multiple browsers is to create different virtual machine configurations using VMWare.

See: http://civicactions.com/blog/2009/may/24/building_ultimate_cross_browser_testing_system

IE6 is buggy, but not for a long time!

http://ie6countdown.com/