styling slide show arrows

Hi,

I am using the following lines of css to style the slideshows navigation arrows on http://utabewegt.de/willkommen:

#top .avia-slideshow-arrows a {
color: #fff;
display: block;
font-size: 10px;
height: 30px;
line-height: 31px;
margin-bottom: 0;
margin-left: 15px;
margin-right: 15px;
margin-top: 30px;
overflow-x: hidden;
overflow-y: hidden;
position: absolute;
text-align: center;
text-decoration-color: -moz-use-text-color;
text-decoration-line: none;
text-decoration-style: solid;
text-indent: -600%;
top: 50%;
visibility: visible;
width: 30px;
z-index: 99;
}

This does a great job regarding the intended size of the box around the arrows, but all of a sudden, the arrows are gone. The goal was to reduce box and arrow size by at least 50%. I have tried to change all values, but the arrows are still missing.

Thanks for your advice ;-)

Cheers, Sebastian.