Hi
Use <a href="javascript:popup('http://domain.com')">click to open popup</a> in template tpl or <literal class='html'><a href="javascript:popup('http://domain.com')">click to open popup</a></literal> in ezxmltext fields.
or define a custom tag:
http://ez.no/products/ez_publish/documentation/reference/xml_tags http://ez.no/products/ez_publish/documentation/customization/components/datatypes/ezxmltext/custom_tags