Can you believe how big the Web has become? Some estimates put the number of web pages at 200 billion. Finding the right information, as I've discussed before, is only going to become harder as the information continues to pile up. Vertical search engines are one new way of addressing this information bloat. Search engines, like Google, are our primary tool these days. Google currently indexes about 10 billion of those pages but they're aiming to hit 100 billion, so they're doing a pretty good job of finding what's out there and making it available to us.

Google's dominance in search also puts them in a great spot to excel in paid advertising. Google AdWords is the only place I do pay-per-click, for example.

What's the future hold, though? What will happen when there are 1 trillion web pages? Will Google be able to keep up? I'm sure they'll hold there own, but one emerging trend to watch is the development of "vertical search."

The main premise of vertical search is searching within a specific category or "vertical." By using a search engine specifically-developed for a single vertical, more accurate and more relevant results are attainable. Using a generic, Internet-wide search like Google will of necessity require some trade-offs in accuracy.

Here are a few examples of vertical search engines:

Technorati: searches only in blogs.

Riya: searches only for images.

As vertical search continues to gain traction, advertising on these tools will also gain traction. Keep your eye on the vertical search phenomenon and watch for search engines that are specific to a vertical in which you have one or more clients. Advertising for your clients on these search engines may deliver a very targeted audience. For more reading on vertical search, click here.