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

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!

yes i have restart my vps see this
screenshot

Do you have a firewall running? Please post the output of sudo iptables-save and sudo ufw status.

kamain7
i think there is something wrong wiith my firewall iptables please take a look at this
screenshot

i am using centos this command is not working
sudo ufw status

What control panel are you using? Try starting the iptables service or checking if there were any errors.

i am using kloxo and i dont know how to start it

Thanks Kamal i fix the problems and my websites are now working fine because of your advice i check and run the iptables
thanks to everyone.