Real and Imagined Errors in Google Sitemap Feeds
When you upload your XML sitemap feed to your server -- especially if it's GZipped -- don't expect it to look pretty. I got a nervous call from a client because when he called the XML feed URL in his browser, he saw this:
While it looks like an error, it's really not. Not in the traditional sense, at least. The error here is that your browser (in this case, Firefox) isn't able to view the file without a little help -- specifically, a stylesheet that tells it how it should look to human viewers.
The bottom line is that this message doesn't mean that engines can't read your XML feed -- only that you can't see it. To see whether Google can process it, for example, check the Sitemap Summary report. For some reason, this report isn't in the main GWT left nav. To find it, you need to click the "Details" link at the far right of the Sitemap Overview report. When you click that link, here's what you see:
Real sitemap errors do exist, even in the example I used above. In this case, I've inadvertently included in the sitemap a URL that I also excluded via robots.txt. So I'm sending Google a mixed message there. Fortunately, the robots.txt file overrides the URL's inclusion in the sitemap, so it ends up being more of a gentle nudge than a true, crippling error. If the error doesn't specifically say that the sitemap is invalid and unreadable, then it's probably not.