internal server error / 500.shtml not found
 

I have a problem a few days ago and still I can not solve, when I open the forum message appears internal server error 500, and when I go to cpanel to check about it from logs error I found this message

File does not exist: /home/user/public_html/500.shtml

how i can solve it now

Note that I did not do any modifications on the site.