function CheckRes() {

resolution = document.body.clientWidth;

  if (resolution >= 1152 - 20)
    document.write("<a href='index.php'><img src='bilder/jpg_1152/logga.jpg' border='0'></a>");
  else if (resolution >= 1024 - 20)
    document.write("<a href='index.php'><img src='bilder/jpg_1024/logga.jpg' border='0'></a>");
  else if (resolution >= 800 - 20)
    document.write("<a href='index.php'><img src='bilder/jpg_800/logga.jpg' border='0'></a>");
  else
    document.write("<a href='index.php'><img src='bilder/jpg_800/logga.jpg' border='0'></a>");

}
CheckRes();