set font-size in combo options in gird

Suite and Optimus Suite 5
#1

How to set font-size in combo options in gird?
I tried to change the font-size in dhtmlxgrid.css
.dhx_combo_select{
font-family:Arial Black;
font-size:20px;
}
but that didn’t work.

#2

In my code, I set the Skin:
mygrid.setSkin(“dhx_skyblue”);
so I also change the code in dhtmlxgrid_dhx_skyblue.css
where :
.dhx_combo_select, .gridbox_dhx_skyblue .dhx_combo_edit, .gridbox_dhx_skyblue .dhx_textarea{
font-family:Arial;
font-size:14px;
}

but nothing has changed.
Can’t set the height of the combo as well.
please help.