Solution idea

Hammer of thor

Login

Username: natas3
Password: 3gqisGdR0pjm6tpkDKdIWO2hSvchLeYH
URL: http://natas3.natas.labs.overthewire.org

Doc

What is inspect element?
Inspect element is a feature of modern web browsers that enables anyone to view and edit a website’s source code, including its HTML, CSS, JavaScript, and media files. When the source code is modified with the inspect tool, the changes are shown live inside the browser window.
How is a webpage structured?

Solution

By inspecting the page, you can see a text snippet that says : 

<!-- No more information leaks!! Not even Google will find it this time... -->

So that makes me start thinking about search engines. In a nutshell the robots.txt file on a webpage tells search engines which directories not to enter.
Robots.txt directory: 

User-agent: *
Disallow: /s3cr3t/
After that, by navigating to the s3cr3t tab, the information for natas4 should be present there.
/s3cr3t/users.txt: 
natas4:QryZXc2e0zahULdHrtHxzyYkj59kUxLQ