Hi there,
After get getting all set up files ready on /var/www/webim, i had hard time installing the app because I was getting the blank page when going to http://<yourdomain>/webim/install/....?!
So, how i resolved it.
I change the premission for /install folder to chmod 755 install/ instal/* - linux
I was missing the php5-mysql extension.
- install: php5-mysql, on linux: #apt-get install php5-mysql
If you webim folder is located on /var/www then on the /libs/config.php file the $webimroot = ""; should be empty.
And that's it, if you get a blank page while installing.
Hope it will help