There are many ways to do it. Range from very easy to almost impossible, depend on what have you done.
I suggest you do try to fix your issue. Can you provide more information? What was the error message? What features have you enabled that cause this problem? Can you login? Can you use File Manager (cPanel) or FTP to access your website? …
Revert Setting:
1. The Easiest
Restore from your backup. Do you have any backups? If no, then bad news. If yes, the next question: Do you know how to do it?
2. The Not Very Easy
These are the things you can try if you can’t login to your website:
http://wordpress.org/support/topic/wp-loginphp-7
http://wordpress.org/support/topic/site-eror
3. The Hard
If you ever enabled the Change wp-content feature, oh what a bad news, you need to have database and programming knowledge to fix it. I personally not dare to fix such case.
4. Others
There are many others you can do, but depend on what issue you’re facing, what have you done, and many things …
