Customize format of category pages


I’m trying to customise the format of my category pages to display posts in a certain way. This CSS code does the trick:

 #blog .blog-post .blog-post-entry {
    width: auto;
    margin: -150px -20px 0px 250px;

This code changes the format for the intended pages, but also for two additional pages I have which I need they remain with the original format.
I tried writing this additional code after reading this post ( “” ) to reset the format for those two pages but it doesn’t seem to have any effect:

#post-190 .blog-post .blog-post-entry, #post-184 .blog-post .blog-post-entry{
	  width: 100%;
    margin-bottom: 0px;
    margin-left: 0px;
    margin-top: 0px;

I also tried this tutorial ( “A Detailed Guide To A Custom WordPress Page Templates — Smashing Magazine” ) in which it explains formatting an specific page can be done by creating a template and modifying the class site-content from the page.php but I that class doesn’t seem to exist in Illdy’s page.php.

Any idea on how to proceed?

Please help!