Check if Apache is running:

service httpd status

or

service apache2 status

Thanks for reply when i run
service httpd status command i see this
httpd (pid 5345) is running…
i am using a monitor when my site is down they send me an email here is it
PROBLEM Alert
Service: HTTP
URL: http://www.mydomin.net
Name: www.mydomain.net_http
Group Name: Default
Date/Time: 7-19-2015 14:31:05 (GMT + 5)
Additional Information: HTTP CRITICAL - Connection timed out. IP .238..***
Failures From: Germany, US-MID

You could have known about this issue 29 minutes ago.

email 2

RECOVERY Alert
Service: HTTP
URL: http://mydomain.net
Name: mydomain.net
Group Name: Default
Date/Time: 7-20-2015 03:05:27 (GMT + 5)
Additional Information: HTTP OK HTTP/1.1 200 OK - 0.072 second response time. IP 178...***
Downtime: 2 minute(s) 35 second(s)

What size Droplet are you using? If you’re on the $5/mo Droplet you should upgrade to the $10/month option or better, especially with a WordPress installation.

Have you tried rebooting your droplet? Doesn’t matter whats the size of your droplet, upon restart, everything starts from zero, unless there is some configuration error or accidentally broken security parameter!