$("#navigation .about").hover(
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/aboutwelcome.jpg)"); 
  }, 
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/"+navbg+")"); 
  }
);
$("#navigation .whychooseus").hover(
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/HPIM5961.jpg)"); 
  }, 
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/"+navbg+")"); 
  }
);
$("#navigation .structural").hover(
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/HPIM5968.jpg)"); 
  }, 
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/"+navbg+")"); 
  }
);
$("#navigation .mechanical").hover(
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/HPIM5962.jpg)"); 
  }, 
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/"+navbg+")"); 
  }
);
$("#navigation .refinish").hover(
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/refinish.jpg)"); 
  }, 
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/"+navbg+")"); 
  }
);
$("#navigation .detail").hover(
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/detail.jpg)"); 
  }, 
  function () {
    $('#navigation').css("background-image", "url(images/header_bg/"+navbg+")"); 
  }
);