Coupon Code: Remove border

Hello, please see the screen shot which shows a very subtle grey border around the field. This field is subject to the following custom css:

#coupon-header {

    white-space: nowrap !important;

}

Could you let me know what I could do further to remove the border?  Thanks!

You can inject this CSS code:

#coupon-container{

    border : none !important;

}

Instructions here:

How-to-Inject-Custom-CSS-Codes

It should look like this: