HTML Validator extension for Firefox and XHTML Strict

A quick tip for using the HTML Val­ida­tor exten­sion for Fire­fox to help debug XHTML Strict doc­u­ments… use ‘Ser­i­al’ mode. So far it has found more than the default mode, and is a great time­saver com­pared with val­i­dat­ing via the w3.org val­ida­tor.