To enable headlines (h1, h2,…) in Typo3 different solutions exist.
One that allows a clear definition of the line break within a headline is to change the header field in the page properties from a simple text field to a textarea. Furthermore, the page rendering has to be changed to render a
tag for the line break character in the textarea.
Add the following line to the file typo3conf/extTables.php
t3lib_div::loadTCA('tt_content');$TCA['tt_content']['columns']['header']['config']['type'] = 'text';
Furthermore, add the following code to the setup in your templatr to adopt the rendering
lib.stdheader.10.setCurrent.br = 1
This solution has been found in the German blog entry of Thomas Hirt http://www.thomas-hirt.at/blog/detailansicht/datum/2008/07/30/typo3-mehrzeilige-ueberschrift-und-zeilenumbruch.html