@hansiwansi
Do you see any errors in Firefox or just a blank webpage? If it's just an empty page try taking a look at the source code (right click in the page and select View Page Source). Is there html code, or not?
I've also occasionally had the white page but I've noticed that in the tab it'll say "Just a moment".
This would either be the site itself, or cloudFlare getting stuck on something.
@hansiwansi Like I said before, check the source code to see the server's response. No response usually triggers Firefox's own error screen. Other than that, try disabling extensions or reinstalling Firefox.