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Your original question had two URLs, one of where the "=" was replaced with "%3D". If that was an actual crawled URL (and not a copy-and-paste error), then it's likely coming from bad links within your own site. That's malformed, so you should definitely check it out. A desktop crawler like Xenu or Screaming Frog could help track down the culprit: http://www.seomoz.org/blog/crawler-faceoff-xenu-vs-screaming-frog