Set 1 column post to zero

I need help to remove the firsts big post inside category.
can u help me to set the first post in category to 0 and leave only 2 column layout for articles?

thanks in advance (i hope u understand my problem becaus my english is orrible!)

Hi,

Could you please provide me with a URL to your website, either here or via PM (click the “Private Message” text underneath my avatar) so that I may analyze it?