Webfig Not Working

I am using 450g Router version 5.7 .when i type the router ip address /webfig/ its not displaying any page . Is any necessary configuration required to enable Web fig

Yes. It needs to be enabled in the configuration, accessible for the address range, and not blocked by firewall rules. The following CLI command will show if it is enabled, the port and allowed addresses:

/ip service print detail

Also note that for the default configuration webfig is NOT accessible from the WAN port (e.g. ether1 on a RB7xx series router). So make sure that your PC is plugged into one of the LAN ports (ether2 - ether5).