How to merge the hrml and CSS files using notepad?

Answer 1

Use link tag inside head tag
<link rel="stylesheet" type = "text/css" href="./style.css">
You can have a custom name for your css file.
You can have relative path for your tag....
Don't often use absolute paths for linking files
Files can be in different folders such a you can have html in html folder and css file in css folder....
You can access them by relative paths......

Answer 2

Ist of all put both files in same folder

Add

<link rel ="stylesheet" src= your file name.css>

Inside the head tag