WEBO Site Speed up Causing Aesthetic Problem

I’ve got WEBO Site Speed Up installed on my site www.blockshop.co.za - but when enabled it caused the Top Menu to display incorrectly. WEBO says I need to probably exclude the .css file associated with the Top Menu to correct this…

Anybody know what file this is? I’m running a slightly modded version of the Toy Store skin.

Thanks in advance - I’d really appreciate any help!