function DropDownMenu(tab,container) {
    this.tab        = document.getElementById(tab);
    this.container  = document.getElementById(container);
    this.timeout    = null;
    this.className  = null;
    
    var self = this;
    this.tab.onmouseover = function() { self.Expand(); }
    this.tab.onmouseout = function() { self.timeout = setTimeout(function() { self.Contract(); },500); }
    this.container.onmouseover = function() { self.Expand(); }
    this.container.onmouseout = function() { self.timeout = setTimeout(function() { self.Contract(); },500); }
    this.Align();
}

DropDownMenu.prototype.Expand = function() {
    clearTimeout(this.timeout);
    if(this.className == null)
        this.className = this.tab.className;
    this.container.style.visibility = 'visible';
    this.tab.className = 'hover';
}

DropDownMenu.prototype.Contract = function() {
    this.container.style.visibility = 'hidden';
    this.tab.className = this.className;
}

DropDownMenu.prototype.Align = function() {
    this.container.style.left = this.tab.offsetLeft + 'px';
}