@-moz-document url-prefix(https://www.google.com/reader/view/?hl=en&tab=wy) {
#selectors-box{display:none !important;}
}

@-moz-document url(http://www.google.com/reader/view/?hl=en&tab=wy#overview-page) {
#selectors-box{display:none !important;}
}