502 bad gateway nginx when trying to access chef-server ui installed on ec2 ubuntu 12.04

502 bad gateway nginx when trying to access chef-server ui installed on
ec2 ubuntu 12.04

i installed chef server on ec2 ubuntu 12.04, everything is installing
perfectly and chef-server-ctl test shows no error . But when I try to
access the web ui am getting 502 bad gateway error.