Atlast the sitemap for this blog has been accepted by google. For the past two weeks I had been trying to register sitemap for this blog but I was getting unsupported file format error.The reason for that is sitemap has to placed under the root directory. Though my blog is under the directory /blog I had to place the sitemap under the root directory. The error message was bit confusing.though.
For wordpress there are plugins available to generate the sitemap for the blog. The popular one is Arne’s Google Sitemap Generartor .