Template:MediaWiki URL rules

URLs must begin with a supported URI scheme: http:// and https:// will be supported by all browsers; irc://, ircs://, ftp://, news:, mailto: and gopher:// will require a plugin or an external application and should normally be avoided. IPv6 host-names are currently not supported.

If URLs in citation template parameters contain certain characters they will display and link incorrectly. Those characters need to be percent-encoded. For example, a space must be replaced by %20. To encode the URL, replace these characters:

sp	"	'	<	>	[	]	|	}
%20	%22	%27	%3c	%3e	%5b	%5d	%7c	%7d

Single apostrophes do not need to be encoded; but unencoded multiples will be parsed as italic or bold markup. Single curly closing braces also do not need to be encoded; but an unencoded pair will be parsed as the double closing braces for the template transclusion.