Advertising placement question

I would like to make my site commercial which I know requires adverts.

Does it have to be a banner, or are side adverts acceptable?

You may use any format available, there's no restriction about that.

Thank you for the response.

Is there a way to modify the position values? I can't find where to specify position: absolute, top and left values so it doesn't end up on the bottom.

Using absolute positioning is not a good idea. You should just place the code where you want the banner to be displayed.
If you still have problems please provide the URL of the page you're working on and tell us where you want to place the banner.