function change1()
  {
  document.getElementById("link1").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-2_01.jpg)";
  document.getElementById("link2").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_02.jpg)";
  document.getElementById("link3").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_03.jpg)";
  document.getElementById("link4").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_04.jpg)";
  document.getElementById("link5").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_05.jpg)";
  
  <!--document.getElementById("box1").style.display = "block";-->
  <!--document.getElementById("box2").style.display = "none";-->
  <!--document.getElementById("box3").style.display = "none";-->
  <!--document.getElementById("box4").style.display = "none";-->
  <!--document.getElementById("box5").style.display = "none";-->
  <!--document.getElementById("box6").style.display = "none";-->
  
document.getElementById("link1a").className="black"; 
document.getElementById("link2a").className="menuwhite"; 
document.getElementById("link3a").className="menuwhite"; 
document.getElementById("link4a").className="menuwhite"; 
document.getElementById("link5a").className="menuwhite"; 

  }
function change2()
  {
  document.getElementById("link1").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_01.jpg)";
  document.getElementById("link2").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-2_02.jpg)";
  document.getElementById("link3").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_03.jpg)";
  document.getElementById("link4").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_04.jpg)";
  document.getElementById("link5").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_05.jpg)";
  
  <!--document.getElementById("box1").style.display = "none";-->
  <!--document.getElementById("box2").style.display = "block";-->
  <!--document.getElementById("box3").style.display = "none";-->
  <!--document.getElementById("box4").style.display = "none";-->
  <!--document.getElementById("box5").style.display = "none";-->
  <!--document.getElementById("box6").style.display = "none";-->
  
document.getElementById("link1a").className="menuwhite"; 
document.getElementById("link2a").className="black"; 
document.getElementById("link3a").className="menuwhite"; 
document.getElementById("link4a").className="menuwhite"; 
document.getElementById("link5a").className="menuwhite"; 
  }
function change3()
  {
  document.getElementById("link1").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_01.jpg)";
  document.getElementById("link2").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_02.jpg)";
  document.getElementById("link3").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-2_03.jpg)";
  document.getElementById("link4").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_04.jpg)";
  document.getElementById("link5").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_05.jpg)";
  
  <!--document.getElementById("box1").style.display = "none";-->
  <!--document.getElementById("box2").style.display = "none";-->
  <!--document.getElementById("box3").style.display = "block";-->
  <!--document.getElementById("box4").style.display = "none";-->
  <!--document.getElementById("box5").style.display = "none";-->
  <!--document.getElementById("box6").style.display = "none";-->
  
document.getElementById("link1a").className="menuwhite"; 
document.getElementById("link2a").className="menuwhite"; 
document.getElementById("link3a").className="black"; 
document.getElementById("link4a").className="menuwhite"; 
document.getElementById("link5a").className="menuwhite"; 
  }
function change4()
  {
  document.getElementById("link1").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_01.jpg)";
  document.getElementById("link2").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_02.jpg)";
  document.getElementById("link3").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_03.jpg)";
  document.getElementById("link4").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-2_04.jpg)";
  document.getElementById("link5").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_05.jpg)";
  
  <!--document.getElementById("box1").style.display = "none";-->
  <!--document.getElementById("box2").style.display = "none";-->
  <!--document.getElementById("box3").style.display = "none";-->
  <!--document.getElementById("box4").style.display = "block";-->
  <!--document.getElementById("box5").style.display = "none";-->
  <!--document.getElementById("box6").style.display = "none";-->
  
  document.getElementById("link1a").className="menuwhite"; 
  document.getElementById("link2a").className="menuwhite"; 
  document.getElementById("link3a").className="menuwhite"; 
  document.getElementById("link4a").className="black"; 
  document.getElementById("link5a").className="menuwhite"; 
  }
function change5()
  {
  document.getElementById("link1").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_01.jpg)";
  document.getElementById("link2").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_02.jpg)";
  document.getElementById("link3").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_03.jpg)";
  document.getElementById("link4").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-1_04.jpg)";
  document.getElementById("link5").style.backgroundImage="url(http://www.bizlink.com.sg/images/menu-2_05.jpg)";
  
  <!--document.getElementById("box1").style.display = "none";-->
  <!--document.getElementById("box2").style.display = "none";-->
  <!--document.getElementById("box3").style.display = "none";-->
  <!--document.getElementById("box4").style.display = "none";-->
  <!--document.getElementById("box5").style.display = "block";-->
  <!--document.getElementById("box6").style.display = "none";-->
  
  document.getElementById("link1a").className="menuwhite"; 
  document.getElementById("link2a").className="menuwhite"; 
  document.getElementById("link3a").className="menuwhite"; 
  document.getElementById("link4a").className="menuwhite"; 
  document.getElementById("link5a").className="black"; 
  }