Google Blog Search...

Google has unveiled a website that lets people search web journals or blogs.

Google says that the software powering the the search site will index all weblogs not just the ones published on (the Google-owned) Blogger.

Further, the index only holds blog postings from June 2005 forward but Google said it was working on ways to add older posts.

I wonder how Google knows a site is a blog rather than some other type of site?