properties of the selector

Not much to go off of, but I'm guessing you're using the CSS Designer and aren't seeing the full list of properties when you go to a selector you've already added?

If that'st the case, in the CSS Designer at the top of its Properties sub panel, uncheck "Show Set" and you should regain DW's full list of CSS properties.

With the "Show Set" box checked, only the properties you currently have set for the selector will show as available...

Unchecking it brings back all options...

1. In CODE view, delete the old selector. 

2. Create a NEW selector and add whatever properties you need.