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The best approach is the command-line utility curl. Using this tool you can submit GET and POST data easilly.
--> submit POST data
set remoteApp to "http://www.server.com/app.cgi"
set URLEncodedVars to "var1=jumbo&var2=blank%20space"
do shell script "curl -d " & URLEncodedVars & space & remoteApp
--> submit GET data
do shell script "curl http://www.server.com/app.cgi?var1=a&var2=b"
If you don't know how-to do it, just ask at our BBS!