Warning: This post contains a solution!
Only continue if:
1.) you want to see a possible alternative solution or
2.) you are stuck and need a hint!
Login using given credentials.
The message on the page is:
You can find the password for the next level on this page.
The password for the next level is in the page source code.
<div id="content"> You can find the password for the next level on this page. <!--The password for natas1 is gtVrDuiDfck831PqWsLEZy5gyDz1clto --> </div>