Curl with asp pages....

What are the differences between asp and non-asp pages when you are curling them? Apart from ,as referred to in php.net, you need to urlencode the post values... Do you also need to urlencode the variable names? And if the submit button on the page has javascript:WebForm_PostBackOptions, is that going to cause any complexity? I have a working php curling script which works on many sites, but this asp page returns error from the server (Error Tracking Code: from server). I have seen problems described on the internet with asp but apart from urlencode tip and that you need to submit the hidden VIEWSTATE etc variables, I have not seen any other tips. I previously got just the input page, so getting the error is actually progress, which I got once I urlencoded the inputs, but clearly the inputs don't make sense to the script somehow and suspect there is some general differences between asp and non-asp pages for this purpose. John