My site stopped opening

[SpyCam]

Well,
one of the Mods emailed me telling me the site is not working.
I wrote to techs that administrate the server side stuff to take a look at what could be wrong with it. They say that they see a problem with global.php or some of the includes. It is just hanging and not bringing any results. It happens both from Apache and from command line.
What PHP settings could affect such problem, if you know, what could we do to fix the problem? Maybe you know what section of the manual could have something that would be helpful in my case?

[Mark.B]

Please could you supply more information on what the site is actually doing?
Error messages
What actually happens when you try to load the site
Is it all pages or just certain pages?
Does the AdminCP work?

[SpyCam]

You can't see the site

[Mark.B]

Did you make any changes to the site immediately prior to it breaking?

[SpyCam]

No, but a week ago techs upgraded server's OS to newer version.

[Wayne Luke]

In your httpd error log, what is the specific cause of the bad gateway?

[SpyCam]

httpd error log is empty

[SpyCam]

So?

[SpyCam]

Found it myself, not much of help here