Whenever porting a HTML template to ASP.NET MVC Core view we have to keep in mind that the path for resources like image , css , scripts should always be coded with '/' before the folder name . For Example -
If you have a template named Clanstech with folder structure as mentioned in below image.
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With code in about.html will be like
<link rel="stylesheet" href="assets/css/aos.css">
In order to use the above css file in ASP.NET MVC Core project with the following structure

We will have to use the following code
<link rel="stylesheet" href="/assets/css/aos.css">
If we dint add '/' before assets folder then it will not load the css file if the user is on suppose /localhost:876/Home/About action/page/view.
To get more idea how file path works , below is the correct usage as shown on this link also https://www.w3schools.com/html/html_filepaths.asp
HTML File Paths
<img src="picture.jpg"> |
picture.jpg is located in the same folder as the current page |
<img src="images/picture.jpg"> |
picture.jpg is located in the images folder in the current folder |
<img src="/images/picture.jpg"> |
picture.jpg is located in the images folder at the root of the current web |
<img src="../picture.jpg"> |
picture.jpg is located in the folder one level up from the current folder |
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ASP.NET MVC Core, HTML5
Porting, HTML, ASP.NET MVC Core