How can I tell if my site has been banned?

There is no real way to tell if your site has been banned from a search engine. If your site was listed and then suddenly disappears, it might be reasonable to assume the site was banned. Normally only sites that engage in some kind of spamming or poor practices get banned. For example, if you have used hidden text, URL cloaking, or been part of a link farm, then it is possible your site would have been banned. There is not usually a way to get re-indexed once a site is banned.