This is a bug that comes from the past directly to b2evo 3.1 beta:

http://forums.b2evolution.net//viewtopic.php?t=15660

As you can see in that thread, EdB wrote a small and effective hack, but it never made into production.

That's why now you see this ugly layout:

http://www.lalaurette.com.ar/blog/index.php/flog/?disp=mediaidx