Thank you for the reply. I went to study a little more and found that the CSS class of Announcement titles is in fact .SubHead in the portal.css file. I found exactly the same class name in my skin.css too, and after testing noticed that settings in portal.css rule over the ones in skin.css if a particular class name is found in both files.
The comments explaining the classes in portal.css seem to be a mess, please someone correct me if I'm wrong. For instance, portal.css says for .SubHead
/* style of item titles on edit and admin pages */
and the skin.css which I happen to have says incorrectly
/* Used in admin sections */
In this situation, I guess that the classes have to be sought out one by one from the core modules' Install .ascx files, which is quite tedious. In the case of DNN 4.0.3 and Announcements module, this would be the Announcements.ascx file, for example.
Any ideas and/or corrections to this post are most welcome, since I'm quite a newbie to DNN yet.
Regards, Heikki.