As per my post up the top - It depends what server your site is running on - do a quick google search to see where to find the logs for your server setup.
The PHP logs are stored differently on each server - this is a server, php/apache setup not a ss one so you will have to do some research based on your server setup - Heres some quick answers - Are you running your site on a Unix system? then normally the logs are stored at /var/log/apache/php.errors so you would do
tail /var/log/apache/php.errors
In a terimal window to view the logs.
If you are Using MAMP error logs are stored at /Appilications/MAMP/logs/php_error.log
If you are Using WAMP error logs are stored at C:\wamp\logs\php_error.log.
How I know they would be PHP Error Logs? - I dont, Blank Screens normally happen because of a error so its highly likely the PHP error log will have something useful (as we havent got anything useful with the blankpage)