Web Server Goes Offline

hi guys, i got ispconfig running on my ubuntu. I got a problem on my web server cause it goes offline, as I'm trying to restart the services by doin these.

Going Management > Server > Services. Select web Server restart and hit save it wont works, can anyone here give me an idea of what cause the problems, and how can i fix it?

plz bear with me.
regards,

 

Do you have any error messages in your Apache log?
What's the output of

Code:

netstat -tap

?