Error message!

I get this error message when I try to view my index-file. The page has worked fine for a month, but crashed this morning, and this is the only thing that comes up:

Fatal error: Allowed memory size of 8388608 bytes exhausted (tried to allocate 30720 bytes) in /usr/home/hosting/vefritid.is/www/wp-includes/pluggable-functions.php on line 255

Any suggestions?