highlighting non-ascii text

Question

As a non-techie, I would really appreciate your help on this.

I have some files (html) that need to be in pure ascii form to be properly processed. Since these files are produced by humans, every so often non-ascii characters sneak in. Often it is a stray " (curled variety) or something similar that is difficult to find and need to be removed.

I have found text editors (eg. textmate) that can strip out all non-ascii characters, but I need to find one that can highlight where they are, rather than remove them (as I need to remove them from the source and not the html file).

I hope this makes sense and appreciate any assistance you can provide.

Thanks!