How to watch post data

I have implemented paypal button in my asp.net app. When buttons redirect me to paypal and when I pay service paypal redirect me to one 开发者_如何学运维of my pages where I need to get data retrived from paypal. I tried to se that data in firebug but I can't find anything. Is there any way to watch received data?

Check out Fiddler. It allows you to view HTTP traffic including headers.

Edit
Description from the website:

Fiddler is a Web Debugging Proxy which logs all HTTP(S) traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP(S) traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language.

Fiddler is freeware and can debug traffic from virtually any application, including Internet Explorer, Mozilla Firefox, Opera, and thousands more.

When all else fails use wireshark. I'm also a fan of Tamper Data and Paros.

Somethimes I've used the Developer Toolbar of IE... it's very simple... Press F12 and go to the Tab Networking then Start Capturing and when finished you have all data in the Result View. double click on a single request and you get it!

Otherwise the FireBug tools it's quite good!