Changing Warning text

hi, in wordpress multisite, when you go mother site and login using a subdomain site ID, you get the following warning:

"You attempted to access the "yourdomain" dashboard, but you do not currently have privileges on this site. If you believe you should be able to access the "WebTopik Sites" dashboard, please contact your network administrator.

If you reached this screen by accident and meant to visit one of your own sites, here are some shortcuts to help you find your way."

If i want to change the wordings of these txt..what do i do? what file is it under? .please help