remote mount hangs sysstem

[RYAN vAN GINNEKEN]

Is there a way to mount a cdrom or  remote file systems using fstab but 
not having it crash out the system.  example if i have a nfs share set 
up to another machine and that machine goes down the next time i reboot  
my system the machine hangs when it cannot find the share and will not 
allow me to do anything and i have to hook up a monitor and keyboard to 
get it back the same happens when there is an error on a cd rom