Google Webmaster Tools is a free service that provides a wealth of information directly from Google. Once you have verified a site with Google, they’ll give you access to all sorts of information.
Here are just a few features of Google Webmaster Tools:
1. Errors
Google Webmaster Tools will show all sorts of errors with a site. Not only does it show broken links on the site, but also links that are driving traffic to the site for which there is no valid page. Google even tells you pages it knows about but has been restricted from crawling. That’s good to know incase someone accidently blocks to much.

Google Webmaster Tools Error Report
2. Set Site Defaults
Tell Google to show your page with the www or without, set a geographic target and select if you want the images show up in Google’s enhanced image search; aka Google Image Labeler.

Google Webmaster Tools Site Defaults
3. Analyze Meta Descriptions and Title Tags
Google will provide a list of URLs that have duplicate title tags or duplicate meta descriptions as well as if there are pages with to short, or to long, meta descriptions or titles.

Google Webmaster Tools Analyzing Meta Data
4. Top Search Queries
Ever wondered what people search... read more >>