By adjusting your padding to:
padding: 1px 3px 0px;
You can save a pixel of space. The first value represents the top and bottom borders by default, while the second value indicates the right and left borders. A third value specifically refers to the bottom border, and a fourth value refers to the left border.
Another option is to use a 1-pixel image with a repeat as a background instead of a border, positioning it 1px from the bottom to save another pixel or two. However, sticking with a simple border may offer a cleaner look.
If you opt for the image approach, here's how to implement it:
Create a 1px x 1px image in your desired color and apply the following CSS:
border-bottom: 0px;
background-image: url('insert-imageURL');
background-repeat: repeat-x;
background-position-y: -2px;
The repeat property will convert it into a line, and the position rule will adjust its placement relative to the bottom edge of your field. Insert your image URL in the specified field.
This method grants you precise control over the line's positioning within the field.