Check out example codes for "what piece of code do a need to make a website fully mobile compatible accross its every links". It will help you in understanding the concepts better.

Code Example 1

<img 
  src="img_girl.jpg" style="width:100%;">

Code Example 2

<meta name="viewport" content="width=device-width, initial-scale=1.0">

Code Example 3

<h1 style="font-size:10vw">Hello World</h1>

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