I want to track users over cross browsers without login option to perform efficient web analytics. I went through flash cookies, but they don't sound promising! Is there any other way to identify users over cross browsers?
Google Analytics has this very useful feature called "Universal Analytics" that allows Cross-Device-Tracking, and thus Cross-Browser-Tacking. I am afraid that this only works if you let your user sign in, because this is actually what enables GA to recognize a user once he visits your website from a different device/browser, and GA will then show him as one unique visitor in the reports.
Actually, "Log In" is only a name for something the user does on your website to be recognized later. You could, for example, let the user enter an email address without a password and, when he does so on the next device/browser, this would be enough to recognize him. Anyway, the user would not (without further customization of the software/CMS you are using) get back his shopping basket, his wishlist or whatever, which would render this feature pretty useless in my eyes.
For further information, there is a great blogpost by Google's Avinash Kaushik on Universal Analytics, and also on this very feature.