I've been unable to get an acceptable answer from Aweber on this issue, and it seems to me it would be a common question. I get 404 errors when I attempt to pass variables from an Aweber opt-in form to my success pages.
The desired result is personalized "Confirm," "Success," and "Already Subscribed" pages on my WordPress blog. Using the latest version 2.9.2, and even trying it with two or three earlier versions as well, and with different themes and with barebones installations with no other plugins activated.
I copied the script that Aweber provides for passing variables from a submitted opt-in form to the custom pages I listed when configuring said form; I copied this script to my header.php file, and I created the pages with my permalinks set so that they read just as I entered them in the Aweber form generator interface... well here, forget trying to describe everything so technically. Watch this video instead. It shows it a lot better than I can describe it:
I hope someone can enlighten me on how to do this. I would think many people have wanted to do this very thing, yet I'm not finding answers anywhere.