I've a list of empty divs and dynamically inserting a background image – so at first, their background-image: url(); property is completely empty. With some event, it's background-image url loads into the previously empty background-image: url(); tag. The url of the appearing background-image is temporarily stored in the "alt" tag of the div:
<div style='background-image: url();' alt='http://something...'></div>
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I'm doing so to get round corners on several animated gifs without using transparent gifs (no smooth edges).
Question: does Google robots index those images? I could imagine they do because the url is already stored in the html code and not in some external css-file, however not as "img" tag but as "alt" or "something" tag!?