Flush DNS?

[benji21]

Having problems loading a particular website, I can load the website fine with no problems at all on a friends computer using his internet connection and I can load it fine using my iPhone with a different connection (3G).

How would I get this working again? a friend said I should do a DNS flush but I command I have been using doesn't seem to work.

I am running OSX Lion (latest version).

 

[grapes911]

Here is the terminal command:
dscacheutil -flushcache

 

[benji21]

Done that but seem to be receiving unknown command? I have sent you a PM..