function resetClass ()
{
//document.getElementById("content1a").setAttribute("class", "nothing");
document.getElementById("content2a").setAttribute("class", "nothing");
document.getElementById("content3a").setAttribute("class", "nothing");
document.getElementById("content4a").setAttribute("class", "nothing");
document.getElementById("content5a").setAttribute("class", "nothing");
document.getElementById("content6a").setAttribute("class", "nothing");

}
function removeElement()
{
document.getElementById("content_1").style.display="none";
document.getElementById("content_2").style.display="none";
document.getElementById("content_3").style.display="none";
document.getElementById("content_4").style.display="none";
document.getElementById("content_5").style.display="none";
document.getElementById("content_6").style.display="none";
}

function showContent_1()
{
removeElement();
document.getElementById("content_1").style.display="block";
}

function showContent_2()
{
removeElement();
document.getElementById("content_2").style.display="block";
resetClass();
document.getElementById("content2a").setAttribute("class", "current");
}

function showContent_3()
{
removeElement();
document.getElementById("content_3").style.display="block";
resetClass();
document.getElementById("content3a").setAttribute("class", "current");
}

function showContent_4()
{
removeElement();
document.getElementById("content_4").style.display="block";
resetClass();
document.getElementById("content4a").setAttribute("class", "current");
}

function showContent_5()
{
removeElement();
document.getElementById("content_5").style.display="block";
resetClass();
document.getElementById("content5a").setAttribute("class", "current");
}

function showContent_6()
{
removeElement();
document.getElementById("content_6").style.display="block";
resetClass();
document.getElementById("content6a").setAttribute("class", "current");
}