html checkbox display different on IE and Firefox as default just the same as picture above. You can make them become the same by writing the following css codes :

input[type=checkbox]{ /** if you put input without [type=checkbox], this css will effect on your buttons and textboxes too. **/
width: 14px;
height: 14px;
padding: 0;
margin:0;
vertical-align: bottom;
position: relative;
top: -1px;
}