Don't bother if you know nothing about HTML , Learn some basic HTML by clicking here & then see this tutorial you will surely can finish this challenge.
Step:1 Go to HTS Basic mission 3. And read the instruction carefully given over the mission.
Step:2 Instruction says that, sam uploaded a password file ,but this time its not a text file. Let's see what we get from the page source of the challenge.
Step:3 Open page source (CTRL + U or Right click > View Page Source).
Step:4 Find "password" in page source by using CTRL + F. See in below image.
Step:6 Now its very simple, go to
http://www.hackthissite.org/missions/basic/3/password.php & you will find the password.
Step:7 Input that password in mission page. Mission is cleared hurray.