XML AJAX响应开始时的奇怪字符？

I'm making multiple AJAX calls that returns XML data. When I get the data back, my success function (in JQuery) tries to turn the XML to JSON (using a plugin). I was quickly reminded why I can't assume I would be getting VALID XML back from my AJAX request -- because it turns out a few of the XML responses were invalid -- causing the JSON conversion to fail, script to fail, etc...

My questions are:

  1. What is the best way to check for valid XML on an AJAX response? Or, should I just attempt the JSON conversion, then do a quick check if the JSON object is valid?
  2. In troubleshooting the XML, I found that there are a few strange characters at the VERY beginning of the XML response. Here's an image from my Firebug:

Bad XML Response

Should I try to detect and strip the response of those chars or could there possibly be something wrong with my encoding?

Any help is appreciated! Let me know if more info is needed!

The strange characters are the Byte Order Mark and are actually valid XML, you can most likely just strip them without risk in most circumstances.

It's the UTF-8 byte-order mark when incorrectly interpreted as ISO-8859-1.

You can't safely strip this because it's just a symptom of a larger problem. Your content is encoded as UTF-8. Somewhere along the way you are decoding it as ISO-8859-1 instead. If you try to hide the problem by stripping the BOM, you're only setting yourself up for more problems down the line as soon as you start using non-ASCII characters. The only reason things are even looking sort-of right is because ASCII is a common subset of both UTF-8 and ISO-8859-1.