Data and variable transfer

OK this may not be the correct place to ask but maybe someone can help. Related to the Post URL ? How do I see the information passed from my browser to a site? I have httpLiveHeaders for mozilla and that does not provide all the info that I need. Or I am not getting something right. I have been trying to use libCURL on some pages and seem to be having a heck of a time doing so. I think what the problem is that a page posts and is thin passed to JavaScript and .jsp that handles the rest of the pageload sequence. I get an 500 error code every time. When using a browser on the site when you click on the submit link it populates a JavaScript and submits the post but I don't know how to handle that in libCURL. I can make the post structure but the page is posting to itself and thus the JavaScript is handling the data. Is there some way that I can see what the rest of the page is doing aside from the headers? I have tried several packet snuffers but while they can get the traffic I have no idea how to decrypt the information to read it. It is an HTTPS site and I can get the cookie information and such but I don't know where to put it in the filters to make the info decrypt. Any help on this matter would be appreciated.