css overflow - only 1 line of text
If you want to restrict it to one line, use white-space: nowrap;
on the div.
If you want to indicate that there's still more content available in that div, you may probably want to show the "ellipsis":
text-overflow: ellipsis;
This should be in addition to white-space: nowrap;
suggested by Septnuits.
Also, make sure you checkout this thread to handle this in Firefox.