Forum Thread: Sniffing Cookies

i was trying to sniff cookies and to log in without having the USERname and Password
this is what i did:

1. i run the commands for sslstrip
2. i opened Wireshark and i started to capture packets
3. i found the cookie and pasted on "wireshark cookie dump" (firefox/cookie injecor/greasemonkey)

i clicked ok and when i refreshed the website nothing has happened
one of the sites was (http://www.lifehacker.com)
please help me!!!