If you are a Safari user and you have a MobileMe account then you can already synchronize Safari bookmarks between multiple Macintosh computers. But what if you want to synchronize to that corporate sanctioned Windows XP machine in the office that runs only Internet Explorer? What if you also want to synchronize to Firefox, running on another machine? All three can synchronize together in one harmonious bookmarking ménage à trois. How is all of this made possible?Xmarks. Formerly Foxmarks, Xmarks now supports more browsers and runs on more platforms. You store a backup of your bookmarks in the Xmarks cloud (which, yes, means that you’ll need to create an account) and then you…