my safari keeps crashing on my iMac. anyone know why. this keeps happening after 10 seconds or so. any ideas?

SAFARI keeps crashing on my Imac.
I have checked for virus software and appear to have none.

I have checked the automatic safari address that loads, which mysteriously had a ,http/ with a coma infront of the default website address to load on safari. I have changed this so the default website is back to apple without the , before the address.

Can anyone suggest what I do next. I keep getting an error message after 3-10 seconds.