IE 10's -ms-clear pseudo-element, and IE5 quirks mode
I'm working on a legacy web app that requires use of Internet Explorer's 'IE5 Quirks Mode' (set using X-UA-Compatible: IE=5 ). A number of text fields in the app have (app-generated) 'x' buttons to clear the content. In IE10, IE also generates an 'x' button to clear the field, so the user sees two of them. As discussed in this question , you can remove the IE-generated 'x' using the ::-ms-clear CSS pseudo-element. Unfortunately, this appears not to work in IE5 Quirks Mode: styling of the ::-ms-clear pseudo-element shows up in the developer tools as :unknown , and the IE-generated 'x' continues