Copy site to another domain - XML SiteMap wrong and Theme Settings not the same
Go to admin/config/search/xmlsitemap/settings and set the correct domain. If that does not work look at your variable table in database and make sure xmlsitemap_base_url is correct. 
Make sure your folder permissions are correct. If you have caching enabled and some themes need to write temp files inside sites/default/files so make sure permissions are correct and that Drupal can write there. 


If that does not work can you inspect where the styles are coming from using Firebug and also post what theme you are using and I can update my answer.