[Help] Install page is a white page

I want to install elgg on my server.(Redhat Linux Server)

I store elgg to var/www/html/elgg

the first time i go to localhost/elgg/install

it show blank page

what should i do???

PS. I try to do like a http://docs.elgg.org/wiki/White_page#display_errors but it can't solve my problem help me plaese thank you