Installing and upgrading help

hi i could just configured 3 stpes in moodle installation..at the pahe where we set our web location and data directory..when i set all the information like follow..
WEB ADDRESS:        http://localhost/moodle
MOODLE LOCATION: /var/www/html/moodle
DATA DIRECTORY:   /var/moodledata
I ALSO    MADE THE CONFIG.PHP FILE according to instratuion given in config-dist.php file..but when i click on next the following address come in URL
http://localhost/index.php
and a white screen comes out and no further progress...
now what could be the problem at this stage..till now i didnot make any database for moodledata directory...
could anyone plzz let me know hwat actually i did wrong.....
hope to see some help from ur side...
i am very very frustrated now..i have been trying out this for last 15 days ,but could not get any success...plzzzzzzzz

regards....