function toggle_div_fun(id) {
var divelement = document.getElementById(id);
if(divelement.style.display == 'none')
divelement.style.display = 'block';
else
divelement.style.display = 'none';
}
to toggle visiblilty of div element #sectiontohide
This is the div to hide with id = sectiontohide