window.onload= function() {
var tam = 1 ;

document.getElementById("maior").onclick = function()
{
document.getElementById("conteudo").style.fontSize = (tam += 0.1) + "em";
}

document.getElementById("menor").onclick = function()
{
document.getElementById("conteudo").style.fontSize = (tam -= 0.1) + "em";
}

document.getElementById("maior2").onclick = function()
{
document.getElementById("conteudo2").style.fontSize = (tam += 0.1) + "em";
}

document.getElementById("menor2").onclick = function()
{
document.getElementById("conteudo2").style.fontSize = (tam -= 0.1) + "em";
}
document.getElementById("maior3").onclick = function()
{
document.getElementById("conteudo3").style.fontSize = (tam += 0.1) + "em";
}

document.getElementById("menor3").onclick = function()
{
document.getElementById("conteudo3").style.fontSize = (tam -= 0.1) + "em";
}
}