cant login as super user Authentication failure,for a previously accessed password

i cant login as super user using su command ,previously it was successful and i am sure that password is correct,previosly there was an issue by changing file permission of www folder and i follow this link to correct ithttp://sysadminnotebook.blogspot.in/...ssions-to.html after that i cant login as su

Do you have any success with sudo -i ?

NO i can access root as driect login

Logging into a terminal or into your GUI?

You need to give a lot more information for people to help you.

If you are able to log into your normal user, are you able to issue the following command?

sudo passwd root