I created a header (header.html) file to be imported into different pages on my site. It works when I have it only in the WebContent folder, and draws the CSS files, fonts, and
Simply use absolute path for your CSS & JS & Fonts & other assets
How?
Instead of
<link rel="stylesheet" type="text/css" href="assets/css/custom.css">
write
<link rel="stylesheet" type="text/css" href="/assets/css/custom.css">
and make sure if assets
directory is in directory for which point your domain
In many cases absolute paths are better, because You don't have to think how to link to your assets from specific directory, because this path always start from root directory
Here is similar question & answer
providing the folder structure has both user and assets mentioned above in the parent directory simply change
<link rel="stylesheet" type="text/css" href="assets/css/custom.css">
To
<link rel="stylesheet" type="text/css" href="../assets/css/custom.css">
This is a relative link meaning it will go up one structure and go from there.
But you need to consider the location from which file it is called as we don't know your directory structure this is the best we can do with the information you've given.