Sometimes on a suphp enabled server, you may get internal server error for a website and in error log it shows the folowing error;
Premature end of script headers: index.php
SoftException in Application.cpp:422: Mismatch between target UID (99) and UID (502) of file “/home/xxxxxxxx/public_html/index.php
To resolve the issue, check the ownweship and permissions of the files and folders. On a SuPHP enabled server, the file permissions should be 644 whereas the folders should have 755 and the ownership sould be cpaneluser:cpaneluser
If you still have an issue after correcting the permissions and ownership, check the httpd.conf and check the user set for the domain name. If its set to nobody, change it to cpaneluser.
You are done!