After analyzing the dojo.css file I understood, that my main.css file and the dojo.css are the files for generic css statements (just different settings).
The right solution: exclude the dojo.css file.
Now I have the formatting from my main.css file and everything
(except of the dojo TabContainer) is under my controll.
(See the font-size and the font-family on the images).
body{font-family:Verdana;font-size:100%;}
#links{position:absolute;top:10px;right:20px;font-size:75%;}
<link type="text/css" href="css/main.css" rel="stylesheet" /> <style type="text/css"> /* @import "/dojo/dojo/resources/dojo.css"; */ @import "/dojo/dijit/themes/tundra/tundra.css"; </style>
