Error when editing the template style

Hello, when I try to edit the style template displays an error (screen.) what is the problem?

It think XML Dom document support is not installed on your server. You could turn to your server administrator to run necessary scripts on server

Thanks, helped!

Another question, the title of the blog is broadcast of the page-header of the site, as it is open from page-header that would be possible to establish an independent header. Where it is necessary to make changes in what file?
And in general this module is disabled on main?
Thank you

Send link, if we see it we will understand problem better

It is strange that this section does not tied to any of the modules and how to manage it is not clear.
morestuff.ru/