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I guess you're trying to edit a theme's html file?
If so, then you might need to turn off your site check for template modifications.
Go to Administration Menu > Preferences > General Settings >
Check templates for modifications ? Select YES
Turn your site off? Select YES
Go Home, see if it worked. Then come back and select NO on both.
If you see this on a block, then check the cache settings. If the chace lifetime is of 1 day, then select 30sec. check again in 30sec to see if it changed. once it does, set it back to 1 day.
Administration Menu > Blocks
Hope that helps. otherwise, add more detail.