Hi
In Google Webmaster tools my website is referenced via /index.php?sitemap

All has been fine but it is now showing an error "Nested indexing...
This Sitemap Index is referenced by another Sitemap Index"

The error is
Sitemap: /cache_html/sitemap/sitemapindex.xml
URL: /cache_html/sitemap/sitemapindex.xml
URL: /index.php?sitemap

Any ideas why this is happening?

Cheers

John

Well, it is happening because there is the relative ?sitemap url and where the actual file is located in the cache. You probably should use only the static url in your robots.txt and with google webmaster. Originally the ?sitemap did also create the sitemap files, it doesn't anymore because of possible server overload so you have to use the backend tool.
Probably the ?sitemap url should not really be used anymore. Probably a htaccess redirection would be a good idea.

So I should just use www.mywebsite.co.uk/cache_html/sitemap for google webmaster?

I guess I missed the change log

Cheers

John

/cache_html/sitemap/sitemapindex.xml is the index sitemap that contains links to further individual sitemaps (images, albums, Zenpage items) following the standard on sitemaps.org.

?sitemap will still call above file, too, but using both is the old "duplicate content" issue.