Problem changing template of ads

[ChaibiAlaa]

Hello,

I'm using Vbulletin 4.0.3, and I want to make ads (with Advertising integrated system) aligned centre (They are left now). I tried to change style from the database but did not worked, no I did changed it to make files for css (from admin -> styles and language) to know what to edit, and, I edited the fil main-rollup.css which contains those ads parameters, It worked the first time but each time I change anything to ads, it get back like before like my edit was crushed and the original version come back with left alignement !

Please help !