When using URLs in
HTML
content, you should generally only use a few of these URL schemes. When referring to subresources ? that is, files that are being loaded as part of a larger document ? you should only use the HTTP and HTTPS schemes. Increasingly, browsers are removing support for using FTP to load subresources, for security reasons.
FTP is still acceptable at the top level (such as typed directly into the browser's URL bar, or the target of a link), although some browsers may delegate loading FTP content to another application.