your life besides the front door to your home is the window of your Web browser.

That’s why the competition between Microsoft and Mozilla and Apple and Google (and Opera and…) is so intense and so important. If the Internet has defined how you experience computers and the world, the vehicle in which you do it becomes vitally significant.

On Thursday, Netscape founder and Silicon Valley entrepreneur Marc Andreessen declared his backing of startup RockMelt, which is building a new, “different” Internet browser that intends to pair with social networking giant Facebook to extend the “real identity” aspect of that company to Web browsing.

RockMelt is interesting because it was co-founded by Eric Vishria and Tim Howes, both former executives at Opsware, a company that Andreessen co-founded and sold (Howes actually goes further back with Andreessen, to Netscape).

Andreessen, it should be said, also sits on Facebook’s board of directors.

Thanks to its connections, it’s clear that RockMelt will make considerable headway on the Facebook platform. The question — beyond whether they’ll get it right and avoid backlash from the vox populi — is whether Facebook is big enough to leverage significant market share in the general Web browsing market.

That may not necessarily be the company’s goal. But I’ve found that proprietary browsing tactics — from Facebook’s current method of managing external links (an in-house link that reroutes to the intended destination) and its Connect service to that old standby, HTML frames — tend to fall flat.

When people want to surface content, they don’t like hoops to jump through and new navigation schemes to learn. Really, they’re already using a browser if they’re on your site.

But that may not be what RockMelt has in mind.

A New York Times article details what little there is to know about RockMelt at this time:

The policy says that a person could use a Facebook ID to log into RockMelt, suggesting that the browser may be tailored to display Facebook updates and other features as users browse the Web. Another browser, Flock, based on Firefox, already incorporates feeds from social networking sites.

The article goes on to explain how Andreessen respects the browser business model, with Mozilla as an example. But Mozilla recently admitted in another article that it is almost entirely dependent on Google’s payments to survive — and now that Chrome’s in town (on PC, soon Mac, and wherever else thanks to the existing Android and announced Chrome operating systems), those payments may be on the way out.

Monetizing a free product can be difficult, of course. Even when distributionhas been achieved.

It’s hard to say what will come of this partnership with so little known information about it. Still, I have a hard time imagining what a browser would look like that’s integrated with Facebook, short of a home page of, yes, Facebook.com.

If the RockMelt browser exists within Facebook, it won’t be playing on the same field as the other browsers and will prove redundant.

But if it doesn’t — meaning it would be a standalone browser that you fire up just like any other — it not only has to achieve performance and feature and usability parity with the competition (on several platforms, no less), but provide enough integration with Facebook to make a user’s Web browsing experience improved enough to justify switching.

And people tend to be very loyal.

The undercurrent among all this leverage. Microsoft leveraged Internet Explorer well because it held dominance over the operating system at a time when OSes were more important than anything else. Microsoft slipped, and Mozilla gained, partly because it allowed its product to detract from the Web browsing experience. (You could say that instead of a simple hinged door to the web, it was more of a revolving model.) And Mozilla’s pairing with Google became a prescient move as that company grew exponentially.

But now Google’s prepared to throw its weight around and leverage Chrome (the browser) with Android and Chrome (the operating system). Microsoft continues, despite a few setbacks, to push Internet Explorer via Windows. Meanwhile, a renewed Apple is using its growing multiplatform existence (Macs, iPhones, iPods) to push Safari.

All of these companies have multiple channels, as well as domination in one area. With RockMelt, I see the dominant position (social networking), but I don’t yet see the channels.