Simple jQuery function works in every browser but Firefox. What am I missing?

$(document).ready(function() {
    $("span.link").mouseover(function(e){
        $(this.children).css("display","inline");
      });
  });

$(function() {
    $("span.link").mouseover(function(e){
        $(this).children().css("display","inline");
    });
});

$(function() {
    $("span.link").mouseover(function(e){
        $(this).children().addClass('inlineClass');
    });
});