The file path for the CSS files is http://Project/Folder/CSS/
The webpage is in the Folder directory.
HTTP cannot access the CSS files, network Status for both CSS files is 404 because HTTP is using the wrong file path. In console GET http://Project/CSS.
Why is GET showing/using the wrong file path?
With the leading slash (/CSS) you’re telling the server to look at the top of the site for a directory called CSS. Ie, Project/CSS, which is not where you’ve put your CSS files. You have two ways to point to the actual files:
href="/Folder/CSS/File1.css"
or href="CSS/File1.css"
The first is an “absolute path” like your original one, but to the correct location. The second is a “relative path”, because without the leading slash you’re telling the server to look for a folder called CSS in the location of the current html file. So since your page is already in the directory called Folder, it looks there for your CSS directory.
There are pros and cons to each method, but both will work. I’ll suggest using the first one.