function showHideDiv(divToDisplay) {
if (document.getElementById(divToDisplay)) {
//hide everything
document.getElementById('web').style.display = 'none'; document.getElementById('email').style.display = 'none';
document.getElementById('market').style.display = 'none';
document.getElementById('print').style.display = 'none';
document.getElementById('train').style.display = 'none';
//show the one you're passing in the parameter
document.getElementById(divToDisplay).style.display = 'block';
}
}