For Mac OS users, there is a system setting that may not allow you to tab onto several types of elements in a web page. To change this setting:
http://www.airset.com/services/permaLink/event/QKOnvIZPEHTU/13317 ...
http://www.airset.com/services/permaLink/event/JsIgFRExPvKB/12968 ...