When someone enter inside my chat room nick changes automatically to Unidentified how to solve the problem.

here is my chat room
http://runzun.4t.com/blank.html

It means the nick they are trying to use is already registered. They need to pick a new one or identify to nickserv.

Any nick i use in my chat changes
If someone who doesn't have knowledge about coding joins my chat then how he/she gonna stay with his/her chosen nick

If they are using a nick that is registered, and they are not the one that registered it, nickserv will change it after 1 minute each time the switch to it.

If it is their nick, they need to identify, either by entering their password in the box, or by doing /msg nickserv identify password once they have connected.