Use a relative path for the CSS

custom/fic.el

@@ -65,7 +65,7 @@
   (while (re-search-forward "\\[fn:\\([0-9]*\\):\\(.*\\)\\]" nil t)
     (replace-match "@@html:<label for=\"\\1\" class=\"margin-toggle sidenote-number\"></label><input type=\"checkbox\" id=\"\\1\" class=\"margin-toggle\"/><span class=\"sidenote\">\\2</span>@@@@latex:\\\\footnote{\\2}@@"))
   (let ((user-full-name "ovely")
-	(org-html-head "<link rel=\"preconnect\"  href=\"https://fonts.googleapis.com\"/><link rel=\"preconnect\" href=\"https://fonts.gstatic.com\" crossorigin/><link href=\"https://fonts.googleapis.com/css2?family=EB+Garamond:ital,wght@0,400;0,700;1,400;1,700&display=swap\" rel=\"stylesheet\"/><link rel=\"stylesheet\" href=\"https://tre.praze.net/fic/tufte.css\"/>"))
+	(org-html-head "<link rel=\"preconnect\"  href=\"https://fonts.googleapis.com\"/><link rel=\"preconnect\" href=\"https://fonts.gstatic.com\" crossorigin/><link href=\"https://fonts.googleapis.com/css2?family=EB+Garamond:ital,wght@0,400;0,700;1,400;1,700&display=swap\" rel=\"stylesheet\"/><link rel=\"stylesheet\" href=\"/fic/tufte.css\"/>"))
     (org-html-export-to-html)
     (org-latex-export-to-latex))
   (revert-buffer t t)