How can i add my css file to html web page?
 

The important points are rel, media, href. If it will go wrong then your code goes wrong.

In the above code rel means relationship is equal to style sheet.
And the important thing is we should not give wrong path for css file. Here i have created a css folder then i have saved my 'mystyle.css' file then i am pointing that file into this html. If your style sheet will be in your main file only then no need to give any path.

This is the most common method of attaching CSS rules to an HTML document. With this method all of your style rules are contained in a single text file that is saved with the .CSS extension. This file is saved on your server and you link to it directly from each HTML file. The link is just a simple line of HTML that you put in the section of your HTML document, it looks like this: