Duplicate sources.list entry

I am completely new to Linux OS. I received following error. Please help what to do to correct. I tried apt-get update to correct but didn't work. Thank you

W: Duplicate sources.list entry http://ift.tt/1lP4WEX wheezy/contrib i386 Packages (/var/lib/apt/lists/http.us.debian.org_debian_dists_wheezy_contrib_binary-i386_Packages)
W: Duplicate sources.list entry http://ift.tt/1lP4WEX wheezy/non-free i386 Packages (/var/lib/apt/lists/http.us.debian.org_debian_dists_wheezy_non-free_binary-i386_Packages)
W: You may want to run apt-get update to correct these problems