i have heard talk about yahoo xml sitemaps, supposedly they are different from xml sitemaps for google? is that so? and what's the difference? i recall that i had an xml sitemap on one site that google liked, i think, but yahoo was returning some result that said there was an xml parsing error or something like that, though it was a really simple file and i don't think there was an error. i made it with xml-sitemaps.com. and does bing have its own kind of sitemap?