var color1 = "black"
var color2 = "red"

var i = 0

function knipperendeLink(){
   i++;
   if (i==1) color = color1
   if (i==2) color = color2
   if (i > 1) i = 0
   setTimeout("knipperendeLink()", 500)
   document.getElementById("knipperendeLink").style.color = color
}