I found some error in httpd error log like seen below:
Unsupported marker type 0x4b Unsupported marker type 0x50 Unsupported marker type 0x50 Unsupported marker type 0x50 Unsupported marker type 0x50
Can somebody help me fix these errors?
This appears to be caused by ImageMagick, from googling "Unsupported marker type", you get a whole raft of bugs that are ImageMagick related.
I'm going to make a wild guess, and say that one of the scripts that your Apache is serving makes calls to ImageMagick, either in PHP, Perl or Python (probably), and that it's trying to handle a corrupt JPEG or other image file.
You should probably check what images it's handling at the time of the error, and then you might have a clearer idea about what's going on.