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Thanks for all your answers, I finally asked a backup to my hosting company and all is working good now !

Great! Glad to hear it.

Good advice from Andrea and Brent. To use multiple sitemaps, do something like this: The main sitemap points to the other sitemap files. You can have up to 50,000 URLs in those files. mine are gzipped This one is sitemap_index.xml <sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"><sitemap><loc>http://yourdomain.com/writermap.xml.gz</loc>  <lastmod>2012-03-15</lastmod></sitemap> <sitemap><loc>http://yourdomain.com/mainmap.xml.gz</loc>  <lastmod>2012-03-15</lastmod></sitemap> <sitemap><loc>http://yourdomain.com/201201.xml.gz</loc>  <lastmod>2012-03-15</lastmod></sitemap></sitemapindex> <sitemap><loc>http://yourdomain.com/201202.xml.gz</loc>  <lastmod>2012-03-15</lastmod></sitemap> Here is a tip: Google will index some of those pages and some it will not index. If you have 5,000 urls in one sitemap and they only index 4957 you probably can't work out which 43 URLs they didn't index, so if you make the numbers smaller, it can be easier to discover the pages they don't like. not easy, but easier