Blank Page- Whole Site Down

We have a portion of our website (an online exhibit), that was made using Omeka and Zend by someone who I have been unable to reach. Basically, the website went down. It only returns a blank page. Does anyone have any suggestions for troubleshooting this? I am lost and don't see anything immediately wrong. There are tons of folders and files, and right now, I'm trying to find a needle in a haystack. I need someone with experience with Omeka to help me out, and tell me what to check first. Thanks!

As a first step, you can try enabling error display, this will cause PHP to print an error message explaining what particular problem you're having instead of just a blank page.

In the directory where Omeka is installed, there is a file called .htaccess. At the top of this file, there is a line that reads

php_value display_errors 0

Change the 0 on that line to a 1, so it reads

php_value display_errors 1

Now you should get a more helpful message instead of simply a white screen.

Also, if your server is set up to log PHP errors, it is a good idea to check those logs. PHP often is able to log errors it cannot display on the page.