Log files are great for tracking down issues and getting more information for your troubleshooting
There are several log files and they are accessible by you through various means.
Apache error logs are the most common place you will be able to view scripting errors, 403 errors, 500 errors, and missing or mis-linked pages.
You can access the Apache logs from your cPanel:
Once you are viewing your Apache logs, you can see where some of the errors lie.
FTP logs will show the adding, removal, and modification of files done by the FTP user you are viewing the log of. This is helpful to track down who made a content change.
The FTP log files can also be accessed by cPanel:
Access logs list the visitors your site gets. You can also view the information in various charts and graphs by programs such as AWstats but the raw data can also be accessed: