when your site is up and working optimal.. ping your site from a command prompt and take note of the return time
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C:>ping
http://www.integramod2.comPinging integramod2.com [209.59.200.113] with 32 bytes of data:
Reply from 209.59.200.113: bytes=32
time=29ms TTL=51
Reply from 209.59.200.113: bytes=32
time=31ms TTL=51
Reply from 209.59.200.113: bytes=32
time=38ms TTL=51
Reply from 209.59.200.113: bytes=32
time=30ms TTL=51
Ping statistics for 209.59.200.113:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 29ms, Maximum = 38ms, Average = 32ms
C:>
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Then do the same when the site isn't working... if you don't get a reply, then you have network issue with the host. If you get a reply but a high time value then you have a throughput issue with your host. In either case its the host and you wan't to give them a call. Though I'd recommend just getting a new host to avoid those problems.