Xah Lee, 2010-03-31
This page reports the popularity of web technologies used today. For example, the popularity distribution of different content management system, web dev language/frameworks, visitor tracking packages, javascript libraries, etc.
71% of sites are detected with a known language/framework/technology. Among them, here's a rough breakdown.

51% has javascript. Here's the distribution of known js packages.

72% sites has some sort of visitor tracking tech.

57% of sites have ads.

3% has blogs.

4% uses CMS.

2% sites has ecommerce.

22% has feeds.

4% sites has media.

16% uses CDN. It is used for example to auto find the nearest server to distribute video.

30% sites has widgets.

70% declared a encoding, of which, 60% uses utf-8, 40% uses iso/iec-8859.
Info of this page is from trends.builtwith.com. Another useful site is backendbattles.com