Not necessarily. It depends upon your intention for putting the url in the citation. If it is solely for your benefit to show where you found the source then a web tag can substitute. If your intent is to show a second party where the source is found then a web tag would not work and you would still need to put the url in the citation.
IMHO I would not do either because all the major source players move their data around frequently enough to optimize storage and that breaks both web tags and urls in citations. I put enough information in the citation to be able to find the source and image without a url.