I just installed Supermag theme (free) and all was working fine until I clicked on the POST page to view the post, and I noticed that the CSS of the Navbar there was disturbed and showing the menu in COMPLETE ORANGE color (instead of lower-border Orange).
Thank you so much for using our theme SuperMAg. As your above information, the URL becomes invalid after installing our theme? We think there is no any relation between theme and site URL. Would you please change to the WordPress default theme once and check that the issue will solve or not ? If still the same issue is arise, it will confirm that there will no any issues on theme. Make sure that, you have not edited any line of code too.
If you have any query regarding our theme, please feel free to ask.