Can't open administration panel

Hi, I have installed ejabberd so:

yum install erlang
and then
yum install ejabberd

now I open the browser at URL http://localhost:5280/admin/
but I can't enter: it request me username and password.

I tried as username: admin@localhost
and password: ejabberd

(I think that them are for default...)

but I can't enter.

What is the problem?

thank you...