This is for all of you who have little or no knowledge about domains and sitemaps.
I just finised installing the sitemap plugin by Arne Brachhold. It created a sitemap for me and in no time submitted it to Google Sitemaps. Everything went fine, untill after 4 hours Google told me that URLs in my sitemap are invalid. I spent an hour figuring out whats wrong, then I realized that a little mistake can result in big failures. The thing that bothered me was www.
I submitted the blog path as http://www.navaulakh.com/blog/ but in my WordPress settings my WordPress path was set to http://navaulakh.com/blog/ so all the URLs listed in the sitemap were referring to http://navaulakh.com/blog/*, which according to Google are not the same. So I had to add www.