Sitemap.xml no style information associated

Hello,

My sitemap looks not good and Google Webmaster tools give me error as well 

This XML file does not appear to have any style information associated with it. The document tree is shown below.

<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">

<sitemap>

<loc>

http://bbbbbbbbb/cache_public/sitemap_system_0.xml

</loc>

<lastmod>2015-05-08</lastmod>

</sitemap>

<sitemap>

<loc>

http://bbbbbbbbb/cache_public/sitemap_profiles_0.xml

</loc>

<lastmod>2015-05-08</lastmod>

</sitemap>

<sitemap>

<loc>

http://bbbbbbbbb/cache_public/sitemap_profiles_info_0.xml

</loc>

<lastmod>2015-05-08</lastmod>

</sitemap>

<sitemap>

<loc>

http://bbbbbbbbb/cache_public/sitemap_bx_blogs_0.xml

</loc>

<lastmod>2015-05-08</lastmod>

</sitemap>

<sitemap>

<loc>

http://bbbbbbbbb/cache_public/sitemap_bx_groups_0.xml

</loc>

<lastmod>2015-05-08</lastmod>

</sitemap>

<sitemap>

<loc>

http://bbbbbbbbb/cache_public/sitemap_bx_photos_0.xml

</loc>

<lastmod>2015-05-08</lastmod>

</sitemap>

<sitemap>

What's the error from Google? The XML file isn't meant to be loaded by the user in the browser, so it's safe to ignore the style message.