Website opens or downloads as a text

PHP script file has a format other that .php

It’s possible that you’re trying to run a PHP script inside an HTML file. By default, PHP is processed correctly only in files with a .php extension. It’s possible to turn on PHP processing for files with other extensions: How to turn on PHP processing for HTML files.

Incorrect access rights for files and folders

Check the access rights for website files and folders. Typically, files have ‘644’ rights (rw-r--r--) and folders have ‘755’ rights (rwxr-xr-x). Contact your website developers for more detailed information.

Database connection error ‘Warning: mysql_connect()’

If you see an error message saying «Warning: mysql_connect() [function.mysql-connect]: Access denied for user», this means that your website is trying to access the database with wrong credentials. The solution is described in the article: Database error on the website.