An adequate technique to block Sites.

1. Get Cold turkey program
2. Input you block lists and times (keywords and url 'hotwords' can be blocked)
3. Install Folder Guard pro from getintopcnet
4. Put the cold folder in the restrict section in this program and select visible or hidden but you must select no access or read-only.
5. Put the password in but make it long and encrypt it using online-toolzcom encryption-decryption
6. Take a picture of the encrypted text and save it on your phone.

OR alternatively download DNSJUMPER and select a filter DNS and then lock this in side folder guard.