My MicroB Browser behaves in an unstable way each time I am on facebook or on any page with pictures, and especially when I click on pictures to have a better view of them. On facebook, the behavior makes it so clumsy an uninteresting to use facebook. I disabled javasript in settings in an attempt to solve this problem, but so many other functions, icons and links refused to work when I click on them. Please can someone advice me on what to do in order to solve this problem?

Sounds like it might also be a problem with Facebook. Disabling JavaScript probably won't work as I believe Facebook relies heavily on JavaScript. That in itself means that it will be problematic on mobile devices. Maybe try the "mobile" version of the site (I don't know if it will be any better):

http://m.facebook.com/

As stated above:

There is no escaping Javascript if you decide to use the web version of Facebook.

Alternatives to the regular site are: http://m.facebook.com as well as http://touch.facebook.com.

You might also be interested in the program "Sociality", written by MohammadAG, which is a pretty decent FB-client for the N900.
Check it here: http://wiki.maemo.org/Sociality

MicroB fries on JS-heavy websites.

I find Iceweasel on Easy-Debian much, much more pleasant for web usage on the N900. Could use a natural swipe direction extension, but it'll do nicely.

Also, you may want to overclock.