On IE all fields of Advanced Search have a small x to delete the content of the field when the field has the focus. For the file height/width this is printed on top of the 'px' of the field.
Browser: Internet Explorer 11
This should be solvable with a css rule specific for the internet explorer ("ms-clear") -
This can be tested on sourcelabs, where different browsers can be run, or with a vm for internet explorers