How to change this font in opera under linux?
 

It is the font which in the circle at the upper corner of the picture.

I didn't find a place to change it. I have changed all itmes at the Tools-Preference-fonts, but it didn't work.
Follow the url before, you can find the picture. For I am newbee here, so i can't inser img within five posts.

my.opera.com/forums/attachment.php?postid=660489

Thanks a lot.