1.  Create art for your web site.
2.  Script the art into your web pages, then load it up in a browser.
3.  If the art doesn't look right, simply adjust the sizes or re-create it.

Don't ever create art for your web site then program your whole web site.  Most often what you'll see is utter disaster.  You'll need to visualize what you want the web site to look like, then focus on art.  Once you've got a general idea, you're set.