Error Logs tool are useful when it comes to diagnosing certain issues such as debugging scripts and finding missing files or broken links you may not be aware of.
Locating your Error Logs in Plesk
Login to your Parallels Plesk Panel.
Click on the Domains link in the left hand panel.
Click on the link Open in Control Panel for the domain you wish to view the logs for.
Select the Website & Domains tab.
Click on the Show Advanced Operations link.
Click on the Logs icon.
Here you will see the error.log for your selected domain.
Locating your Error Logs in cPanel
Login to your cPanel WHM Panel.
Click on the Account Information link.
Click on the link List Accounts.
Select the domain you you wish to view the logs for and click on the icon in the cPanel column.
This will open the customer cPanel for that account, under the Logs section click on the Error Log icon.
You will now see the last 300 entries displayed in reverse order.
Locating your Error Logs in Apache
Open a terminal session to your VPS using a client such as PuTTY.
Enter your username and password.
Browse to the directory where the error logs are located.
# cd /usr/local/apache/logs/
Open the error log file.