will a url in a css file count as a back link or even send a bot back to my site after reading a css file?

No No and NO


for one very very simple reason

SE bots don't read CSS files.

ok thanks for that

Two simple reasons, actually...it's not a web page, and therefore a link in a CSS file isn't an actual hyperlink.

though some scripts are crawlable its not indexable...

Even if Google decides to start indexing css tomorrow, it doesn't have links inside it. Some forum software automatically detects urls and converts them to links ... but they aren't the same thing.

Originally Posted by chrishirst

SE bots don't read CSS files.

I think this is not true, google is known to read CSS files to detect hidden text and links, i am sure yahoo also does this. I've even seen my site's CSS file listed in yahoo's site explorer list of pages indexed from my site.

I believe NO. I think it is ignored by spiders... Anyway, is it legal to do that? Isn't it considered as a black hat?

It's not "black hat" to use fully qualified URLs in your CSS. Think

background-image:url(http://www.domain.com/bg.gif);