The tag I had looked like this:

#MSOZoneCell_WebPartWPQ4 td h3 a

I wanted to add a tag on the end so that it looked like this:

#MSOZoneCell_WebPartWPQ4 td h3 a, #MSOZoneCell_WebPartWPQ5 td h3 a

I used this Regex in Sharepoint Designer to do so:

Find

#MSOZoneCell_WebPartWPQ4 {.*$}

Replace

#MSOZoneCell_WebPartWPQ4 \1, #MSOZoneCell_WebPartWPQ5 \1

The “\1″ is called a “Tagged Expression”.  It refers to the part of the value that is tagged in the “Find” syntax.  You tag something using brackets, so in this case “.*$” was tagged, which corresponded to this part of the result ” td h3 a”.  I had about 10 of these, so this saved me a lot of time.