If you are going to create a new browser from scratch and go up against the Google, Microsoft, Mozilla, and Apple, you might as well make it really different. Rockmelt , a company backed by Netscape founder Marc Andreessen which has been under wraps until today , is trying to build a new browsing experience from the ground up. Are they crazy? "The big thing," says Andreessen, "is that the browser world is very much in flux right now." Rockmelt is built first and foremost for sharing. You browse with your friends (the first thing you do is log into Facebook and your favorite friends and their latest status updates are always available along the left rail). And there is a big "Share" button up top, which lets you share any webpage, along with images and a preview, on Facebook. You could call it a Facebook browser, but it really is more than that. I'll get into my full review shortly, but if you want to try out Rockmelt for yourself, be one of the first 500 TechCrunch readers to click this link and you will get an invite before anyone else). The three biggest changes to the browser that you notice with Rockmelt is that it is built around friends, feeds, and search results. The left rail is for friend. The right rail is for sites. And the top rail is for search.