Posting this one just because I had to look it up like 3 times in the last month.  In Dreamweaver I have lots of pages with an HTML tag but something different in the tag like this:
a bunch of stuff that doesn’t change BR549 and some more stuff that doesn’t change

where BR549 is different every time.

This is the RegEx to find it

a bunch of stuff that doesn’t change (.*?) and some more stuff that doesn’t change

This is where to play with it:

http://www.regexr.com/