Assuming public_html is your root:
<link rel="stylesheet" type="text/css" href="/folderX/folderY/css1.css" />
My personal advice is not to interfere with relative paths; they will only kill you when you start moving PHP scripts; or, even worse, when your code is included as part of another script, and you don't know where it is.
The same can be said for links inside CSS (images); itβs not always immediately obvious that relative paths inside CSS files are taken from the location of this file, unlike inline CSS, which uses page layout.
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