function changePage(img){
    changeMenu(img);
    changeContent(img);
}
function changeContent(img)
{
    var imgMain = document.getElementById('contentImg');
    var divParent;
    var imgNew = document.createElement('img');

    if (img == "portfolio") {
        imgNew.src = "imagens/nitroquimica.jpg";
    } else if (img == "internet") {
        imgNew.src = "imagens/apdcrim.jpg";
    } else {
        imgNew.src = "imagens/" + img + ".jpg";
    }

    imgNew.id = 'contentImg';
    divParent = imgMain.parentNode;
    divParent.replaceChild(imgNew, imgMain);
}

function changeMenu(img)
{
    var imgMenu = document.getElementById('headerImg');
    var divParentx;
    var imgNew = document.createElement('img');

    if (img == "portfolio" || img == "internet") {
        
        imgNew.src = "imagens/menu/" + img + ".jpg";
        imgNew.id = 'headerImg';
        imgNew.alt= img;
        imgNew.isMap = "true";
        if (img == "portfolio") {
            imgNew.useMap = "#menuPortfolio";
        } else if (img == "internet") {
            imgNew.useMap = "#menuInternet";
        }

    } else {
        imgNew.src = "imagens/menu/menu.jpg";
        imgNew.id = 'headerImg';
        imgNew.alt= img;
        imgNew.isMap = "true";
        imgNew.useMap = "#menu";
    }

    imgNew.border = "0";
    divParentx = imgMenu.parentNode;
    divParentx.replaceChild(imgNew, imgMenu);
}
//<img id="headerImg" src="imagens/menu/home.jpg" alt="Menu" ismap="true" usemap="#menu" border="0" />