Google recently enhanced the infrastructure that processes sitemaps some days back. This is done particularly to process the sitemaps against certain guidelines, as the team at Google work out interoperability with other tools that use this protocol. Therefore, some of the users can also locate an "unsupported file format" error on the sitemaps which displayed an "OK" status earlier.
It is conveyed that the chances of getting this error are more if the parser doesn't recognize a relevant Sitemap file. Following are some tricks that can be of your help if see an error.
1. Make sure that the file uses the correct header. For a Sitemap file, the header can look like this:
<?xml version="1.0" encoding="UTF-8"?><urlset xmlns="http://www.google.com/schemas/sitemap/0.84">
2. For a Sitemap index file, the header can look like this:
<?xml version="1.0" encoding="UTF-8"?><sitemapindex xmlns="http://www.google.com/schemas/sitemap/0.84">
3. Check whether the namespace in the header is "http://www.google.com/schemas/sitemap/0.84".
4. Also check that the figure comes to 0.84. If it ends in .84, you'll see an error.
5. Ensure each XML attribute is enclosed in either single quotes (') or double quotes (").The quotes should be straight and not curly.
It is stated that the usage of the word processing program, such as Microsoft Word might insert some curly quotes.