Dynamic <title> Tag with Wiki-Title AND Article-Title
Fragment of a discussion from Project:Support desk
Edit the page "MediaWiki:Pagetitle" on your wiki and put the following inside of it:
$1 - {{SITENAME}}
Then on every page the <title> will be the way you want. The "MediaWiki:Pagetitle" wiki page is used as format for the title and $1 is replaced with the wiki page name.
For your wiki it is here: http://www.trainerlexikon.de/index.php?title=MediaWiki:Pagetitle&action=edit
It looks like user "StefanLapenat" on your wiki has changed this in 2005 ([1]).
All you need to do is delete that edit,
.. and then it is good :)