Template:HD/url

URLs containing certain characters will display and link incorrectly unless those characters are encoded. For example, a space must be replaced by %20.

sp " ' , ; < > ? [ ]
%20 %22 %27 %2c %3b %3c %3e %3f %5b %5d
Single apostrophes do not need to be encoded; multiples will be parsed as italic or bold markup

The link button on the enhanced editing toolbar will encode a link.

The URL must start with a supported URI scheme. http:// and https:// are always supported. gopher://, irc://, ircs://, ftp://, news:// and mailto: will create a link and an icon but require an agent registered in the browser.