Fix a warning by merging the two 404 pages

Author: vgvassilev

404.md

@@ -1,10 +1,11 @@
 ---
-title: "Page Not Found"
 layout: default
-excerpt: "Page not found. Your pixels are in another canvas."
-sitemap: false
+title: 404 Not Found
 permalink: /404.html
 ---
 
-Sorry, but the page you were trying to view does not exist.
+# 404 Page Not Found
+
+The page you were looking for was not found.
+If you believe this was in error, please contact <mailto:[email protected]>