Joomla! Documentation™

This field essentially is a text field with the type of url. If a fully qualified url (that is one with a scheme and domain such as http://example.com) is entered and it uses idn (that is uses characters that are non ascii such as ê or Ψ) it will translate the url into punycode prior to saving. This assures that the url will work as intended regardless of environment. If you want to render field data in idn you should wrap it with the conversion method

 JStringPunycode::urlToUTF8($this->contact->webpage)

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Both a url rule and a url input filter can assist with this insuring that valid url data are entered into this field field