function resetClass ()
{
document.getElementById("content2a").setAttribute("class", "nothing");
document.getElementById("content4a").setAttribute("class", "nothing");
document.getElementById("content5a").setAttribute("class", "nothing");
document.getElementById("content6a").setAttribute("class", "nothing");
document.getElementById("content7a").setAttribute("class", "nothing");
document.getElementById("content8a").setAttribute("class", "nothing");
}

function removeElement()
{
document.getElementById("content_1").style.display="none";
document.getElementById("content_2").style.display="none";
document.getElementById("content_4").style.display="none";
document.getElementById("content_5").style.display="none";
document.getElementById("content_6").style.display="none";
document.getElementById("content_7").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");
}

function showContent_7()
{
removeElement();
document.getElementById("content_7").style.display="block";
resetClass();
document.getElementById("content7a").setAttribute("class", "current");
}

function showAll()
{
removeElement();
resetClass();
document.getElementById("content_2").style.display="block";
document.getElementById("content_4").style.display="block";
document.getElementById("content_5").style.display="block";
document.getElementById("content_6").style.display="block";
document.getElementById("content_7").style.display="block";
document.getElementById("content8a").setAttribute("class", "current");
}