Error message when click sub sitemap links

for sitemaps:
sitemap-misc.xml
sitemap-tax-post_tag.xml
sitemap-tax-category.xml
etc....

This page contains the following errors:

error on line 8 at column 14: XML declaration allowed only at the start of the document
Below is a rendering of the page up to the first error.

div[id*="supernova"] .widget-title { background: url("<removed url>") no-repeat 5px 22%; padding-left: 25px; }