Hi -- been using the AuthNet DPM process for about 2 years now. Works great overall... we process a couple hundred orders per day on our site using DPM.
Occasionally, some people have trouble with the response URL and how it parses the good/bad response using the META refresh tag. Evidently, DPM requires a second or so to validate the HTTP headers of the response URL before redirecting to a "declined/invalid card # page" or "receipt page". Some people's browsers/firewalls (very few) do not allow META refresh or they error out on it.
I've tried lots of other techniques to work around it and all of them result in a message from AuthNet that "Your script timed out while we were trying to post transaction results to it.".
Anyone else experience issues with META refresh and come up with a good solution?
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Here is the code I am using: on the response page (# == encapsulated variable)
<html><head><script language="javascript">
<!--
window.location="#redirect_url#";
//-->
</script>
</head><body><noscript><meta http-equiv="refresh" content="1;url=#redirect_url#"></noscript></body></html>