Signup: confirmation after creating a site


After I create a new site appear a page with the message:

Congratulations! Your new blog is ready!

First, I want to know how to translate it, I tried in the wp-signup.php but I could not find it.

After this message appear the username, password and the links to acess the site. I also want to know how to change the code of it. I want to change the css and translte the words.