app to look/view/inspect http traffic...

[bruce]

hi...

i'm trying to figure out what's going on with a site from my browser... does
anybody have/recommend a good "open source" app to see/review the http
traffic going back/forth between my box and the site's server...

my issue is that i can use a browser and i get the html/response within the
browser. when i try to emulate what the browser is doing, using
libwww/mechanize/etc... i get something different. in fact, when i try toto
insert what i believe to be the url/query into a browser url address, i get
a different response...

so i'm looking to actually try to see the http trafffic that goes back/forth
between my browser and the server to track down what's really being sent...

i'd prefer something that's quick/easy to setup and run, that produces a
reasonable output!!!

thanks...

-bruce