CSS Help in Wordpress Site on Archives page

I have a wordpress site and I want an image to float right of the category title and description in the archive page. For some reason the category title and description keeps going underneath the image instead of next to it. I was able to make the image float right in the [login to view URL] - my post page but I don't know why in the archives page it doesn't work and I tried lots of things. Perhaps it could be that there is more complicated php in the archive page than in the post page. I don't know. I have two sites with two different themes, which both have this problem. I think its probably the make thing that needs to be fixed for both to make the image float right. I need someone make the image in the archives page only to float right in these two sites.