[SOLVED] How to create two column in certain pages' content?

I have a code I use for my standard page formatting, it goes like this:

.embed {
width:23%;
float: left;
padding:0 0 0 10px;
margin:0 0 20px 0;
}

Now, I would like to have pages that are divided 50% (two columns).
So, is there a way to apply this code to certain pages only?