2007/8/3, Kokul :
> Ok Now i login as kokul.k. But when a bug is assigned to kokul.k user the

here you say "kokul.k", but further down...

> "The name kokul is not a valid username. Either you misspelled it, or the
> person has not registered for a Bugzilla account."

.... the error message says you entered "kokul". If you want to enter
"kok" and have Bugzilla find it, set the usermatchmode parameter to
"search". If set to "wild", you need to enter "kok%" (I'm not sure --
maybe "kok*" or "kok.*" instead).

If none of this works, it may be that the kokul.k user is configured
to be invisible to you. Check group visibility settings and Bugzilla's
strict_isolation and usevisibilitygroups parameters. For testing, you
can switch usemenuforusers on and see whether kokul.k appears in the
drop-down for users to assign to.