If visitors to your website are getting a file downloaded instead of seeing your website, this is typically caused by an issue with gzip either being enabled when it shouldn't be or disabled when it shouldn't be. 

To resolve this, go into cPanel and select the MultiPHP INI Editor.

Under the basic mode tab, select the PHP INI file for your domain.

Toggle the switch for zlib output compression and then click on Apply.

Clear your browser cache and then try to reload your site again. If you site loads, then you have a plugin that is affecting this setting. Sometimes this can be caused by caching plugins. A lot of caching plugins will need zlib compression turned off as it can interfere. Check with your caching plugin developer for further assistance.