Thanks alot Alfie :)

1. I tried to put your code this in style.css:
.postingheadline { font-size:1.1em; }
it works fine with the post Title after you opened the thread.
(I digged out that the postingheadline is used in thread.tpl.inc)

2. But what I really want is to enlarge the font size of the Title before it is opened, namely, when they are displayed in index.php.

Really appreciating your and Alex's answers, helped a lot in learning the MLF better :)

Regards,

Btw: I logged in with my user name milfan in another computer to reply, but can not reply more, it says: this name is already used by another user, dunno why, so a new name