I grabbed the article below from Google Webmaster Tools' page. Why do i grab this? Because maybe not a lot of peophe have signed up on Google Webmaster Tools. the site how to get the blog friendly with Search Engines.
404 not foundThe webserver returned a 404 error (page not found). This page likely does not exist.
HTTP errors/ 401/407 authentication errorThe page requires authentication. It's likely that you do not intend this page to be indexed. If this page is listed in your Sitemap, you can remove it. However, if you leave it in your Sitemap, we won't crawl or index it (although the page will continue to be listed here with this error).
HTTP errors /4xx error
See RFC 2616 for a complete list of these status codes. Likely reasons for this error are that the webserver didn't understand or couldn't process the request, the request was forbidden, or the request timed out. If the page has moved and requests for it return a status code of 410, you might consider changing the response to return a status code of 301 and permanently redirect the request.
HTTP errors /Domain name not found
The DNS may not have been properly resolving. We could communicate with the DNS server, but couldn't find the domain name.
HTTP errors /Couldn't parse HTTP response
When we tried to access your page, we couldn't parse the response we received from the webserver.
HTTP errors /IP in excluded range
The IP address is in a private address space, reserved for local use (for instance 127.0.0.1). See RFC 1918 for information on private IP ranges.
No Title - Google encountered a general HTTP error
Google encountered a general HTTP error when trying to access this page. Note potential reasons for this error could include any of the HTTP errors listed on this page.
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