The stickiest sites on the web, as measured by comScore, are the portals. For example, people visited the Yahoo! family of sites, on average, nearly once a day. Community, entertainment and news sites followed closely behind, with frequency rates of once every two days.

From a minutes-per-visitor perspective, the portals again came out on top-- the Yahoo sites led here with an average of 11 minutes per visit; they were followed by community sites, led by MySpace.

If you are creating a top portal or a hugely popular community site, you have very little to worry about from a stickiness perspective. But what makes those sites so sticky? Let's take a look.

Yahoo does many things right. They start with a huge stickiness advantage by including a vast amount of content, much of which has integrated itself into people’s basic daily functioning. Yahoo has IM, maps, mail and much, much more.

But in addition to these advantages for creating stickiness, Yahoo does unusually well in several other areas.

The homepage manages to be clear despite the vast quantity of content. It is easy to find any of the many Yahoo sites and applications. Certain areas of the site are AJAX-enabled, allowing for simplicity and richness at the same time. And the content varies from time to time-- though, surprisingly, it doesn't seem to happen very often or very quickly.

It is the small things that create Yahoo’s unique stickiness. For example, the site offers both a Y! toolbar and the ability to set Yahoo as your homepage with one click. If a visitor does either of these things, then Yahoo is virtually guaranteed multiple visits per day.