According to Google, Blogger Web Comments for Firefox is an extension that helps bloggers see what other bloggers are saying about the page they are viewing. Apparently, it's also possible to make your own blog post about it, without leaving the page you're on.
Just a guess: Did you use Firefox previous to 1.5?
If so, it's possible that you might have set your pre-1.5 "xpinstall.enabled" option to false, blocking software installation. This option is no longer exposed in the Firefox Options GUI, so you may need to dig a bit deeper into your Firefox configuration.
Browse to the URL "about:config" and look at your xpinstall.enabled option setting. Double-clicking the option will toggle it from false to true and back.
Too much spam. I don't know why non-link specific URLs are showing up. It doesn't handle dynamic URL accurately. Needs option to disable search on specific domains like Google. Otherwise, its really noisy.