admin ok but site vanished!

[dml311071]

Hi

The strangest thing:

my site www.gravisuk.com/index.php has vanished. I can log into the ftp and the database and see all of the site and database but when I go to the site URL, there is just a blank page!

I was editing the amount of letters used in the product description and whether a category image was shown at the top of the page when I happened to refresh my store page to view the changes.

Nothing, blank page, no source code.... nothing

If I log into the admin, all works fine! can view everything that admin provides.

I have tried resetting the boxes...nothing
and viewed the index.php file nothing appears wrong there

I can't see any other access on the server log. What have I done?

Urgently need help with this one, the site is about to go live.

Thanks in advance

Dave

also this is the link from admin when attempting to view the store (I have enabled SSL in admin):
https://www.gravisuk.com/index.php?main_page=
Also Firefox shows the store is in quirks mode as if there was no DOCTYPE