OK, so SL has three key features that I want to utilize in this proposal: SLURLs, landmarks and teleportation. 

My idea is that an SL user can embed a SLURL in a specific location in-world, perhaps as a script, and the next user can left-click on the script to select one of two pertinent actions: "teleport" or "add as landmark":

• If "add as landmark" is selected, then it will open either as a separate HUD window menu which displays the landmark inventory and various means of landmark management, or, if the option is middle-clicked, as a whole new tab containing the same.
• If "teleport" is middle-clicked (or the script itself can be middleclicked), then the teleportation load can take place in another new tab while the user is still in the previously-open location.
• The kicker: once the new tab is finished loading the view of its own location, the user can then select the new tab and immediately move the avatar’s presence to the new tab’s location, and then move freely back to the older tab with the avatar’s presence following the user to the older tab’s location. You move in, the avatar moves in; you move out, the avatar moves out, and so on.
• The avatar’s behavior across tabs can be optionally switched off if the user simply wants to view another location’s goings-on without the user’s avatar getting involved or, worse, stuck in the middle of such events.

I think this navigation method can work for the following reasons:

• Instead of saying "I’ll be going now, gotta head to Luskwood", it can instead be "gimme a sec, I’m looking in Luskwood as we speak….oh, nevermind, I’m back here at Badwolf’s…nah, its dead there, now I’m up in this space station filled with alien avatars".
• Flying from one place to another can be quicker, farther, multitasked and much more balanced.
• Going from one grid to another and back (or maybe three grids or more in separate tabs) can also be a matter of seconds.
• You wouldn’t have to be automatically logged out of Second Life if one grid is closing for repairs.
• Avoiding griefer attacks while watching (peeking?) the disasters unfold in another tab will either be hilarious or sobering from a distance.

So yes, it is a proposal to make virtual world clients more like modern web browsers without necessarily entailing the embedding of the web inside the virtual world (although current web-browsing capabilities of the SL client may benefit from the above-described virtual world tabbed browsing); it captures the non-linearity of the tabbed navigational experience and fits it upon the virtual world that is much too linear (think "IE6") to navigate fully and smoothly within a multitasking framework.