"Walled Garden" — it conjures up images of a lush, exotic, and beautiful garden isolated from the rest of the world by a high stone wall with a single locked door to limit access. And in many ways, it's an accurate image for the kind of Internet access available through most web-enabled HDTVs.

In the context of interactive television, a walled garden is an Internet portal from which you can only access select websites or information, contained "inside" the walls.

Manufacturers now offer HDTVs with various kinds of built-in Internet access. This web content displays on the TV, either filling the screen, or just taking up a portion of it. Each brand has a slightly different set of websites — or walled gardens — they can access, but there's one thing they all have in common. They don't allow you to surf the entire worldwide web directly through your HDTV.

But a walled garden has one big advantage: since you don't have to sift through the entire web, you can very quickly access what's inside the wall. And manufacturers are making sure that many popular sites are included.

Here's how three companies use walled gardens with their Internet-capable TVs:

Panasonic's plasma TVs with VIERA Cast™ take you to a special menu, which lets you access Amazon Video On Demand, YouTube, Picasa, and receive stock and weather updates.

Sony's Bravia Z-Series TVs connect to a Bravia Internet Video site, which has a mixture of free and premium sites. Their current selection includes YouTube, Amazon Video On Demand, Sports Illustrated, Sony Pictures, Sony Music, Slacker and Epicurious.com.

Many of Samsung's latest generation of 2009 flat-panel TVs feature select content from Yahoo!, such as weather, news and financial updates. You can also access Flickr through the Samsung/Yahoo! walled garden.