There are several ways to randomize post order, i cant exactly remember where it was but i assume you can find it with sth like this: http://www.google.com/#hl=en&source=hp&q=random+site%3Aforums.b2evolution.net&aq=f&aqi=&oq=&fp=cbc2f75bf9d43a8f

However, those hacks "temporarily" randomizes display order, which i mean, when you hit your index.php you got an order;

post8, post15, post2, post6

the next time you hit home, it will be sth like;

post7, post6, post15, post4 etc...

you will get a new random page everytime you visit the homepage, if that is what you are looking for , you are lucky, but if you want a permanent random order, you will have to bump up the other topic :http://forums.b2evolution.net/viewtopic.php?t=20138 asking for a hack/plugin.

Btw, i believe index.php?order=RAND must be an order parameter as well as asc and desc