That's kind of the point. He might have matching cruft in a CDATA section, or (more likely) inside a comment because the web designer decided to move something around but left the old location in place for reference and never cleaned up afterwards. You've handed him a ticking bomb prossibly starting him off with a bad habit and sooner than later that's going to go boom.[1] You don't know what his actual data is so the best answer is the most generally correct one: don't try and wing it handling HTML with regexen, use a proper parser.

[1] – "No boom today. Boom Tomorrow. There's always a boom tomorrow."