function ShowPopUp(alignmentControl, helpPopUp, inPopUp, addBackground, offsetX, offsetY)
{
    var me = this;

    this.AlignmentControl = alignmentControl;
    this.HelpPopUp = document.getElementById(helpPopUp);
    this.InPopUp = false;
    
    if (inPopUp != null)
        this.InPopUp = inPopUp
        
    this.HiddenSelectControls = null;
    this.HeightDiff = 0;
    this.CurrentOpacity = 0;
    
    // Lower number means quicker - 0 will display instantly
    this.PopUpSpeed = 0;
    
    this.AddBackground = false;
    if (addBackground != null)
        if (addBackground == true)
        {
            this.Background = null;
            this.AddBackground = addBackground;
            this.BackgroundAdded = false;
        }
    
    this.OffsetX = 0;
    this.OffsetY = 0;
    
    if (offsetX != null)
        this.OffsetX = offsetX;
        
    if (offsetY != null)
        this.OffsetY = offsetY;
        
    this.IsIE = null;
    this.ShowCloseOnScroll = false;
    this.ClosePopUp = null;
    
    this.HelpImage_OnMouseOver = function()
    {
	    // Display the help pop up
	    me.displayHelp();
    }
    
    this.HelpImage_OnMouseOut = function()
    {
	    // Simply hide the help pop up 
	    me.hideHelp();
    }
    
    this.fadeInPopUp = function()
    { 
        // If pop up speed is 0 set opacity to 100
        if (this.PopUpSpeed == 0)
            this.CurrentOpacity = 100;
            
        // Fade in the pop up by setting the opacity
        me.setPopUpOpacity()
    }
    
    this.setPopUpOpacity = function()
    {  
        if (this.CurrentOpacity <= 100)
        {
            // Set opacity values to work in all browsers
            this.HelpPopUp.style.opacity = (this.CurrentOpacity / 100); 
            this.HelpPopUp.style.MozOpacity = (this.CurrentOpacity / 100); 
            this.HelpPopUp.style.KhtmlOpacity = (this.CurrentOpacity / 100); 
            this.HelpPopUp.style.filter = 'alpha(opacity=' + this.CurrentOpacity + ')';
            
            this.CurrentOpacity = this.CurrentOpacity + 5; 
            
            var me = this;
            setTimeout(function () { me.setPopUpOpacity() }, parseInt(this.PopUpSpeed));
        }
        else
            this.CurrentOpacity = 0;
    }
    
    this.Initialise = function()
    {        
        // Work out browser type
        var agt = navigator.userAgent.toLowerCase();
        this.IsIE = ((agt.indexOf('msie') != -1) && (agt.indexOf('opera') == -1));
    }
    
    this.Initialised = this.Initialise();
}

ShowPopUp.prototype.displayHelp = function()
{
    // Set up background if required
    if (this.AddBackground)
    {
        if (!this.BackgroundAdded)
        {
            this.Background = document.createElement('div');
            
            // Style background div element
            this.Background.style.position = 'absolute';
            this.Background.style.top = 0;
            this.Background.style.left = 0;
            this.HelpPopUp.style.zIndex = '100';
            this.Background.style.backgroundColor = '#FFFFFF';
            this.Background.style.filter = 'alpha(opacity=35)';
            this.Background.style.opacity = 0.35;
            this.Background.style.KhtmlOpacity = 0.35;
            this.Background.style.MozOpacity = 0.35;
            
            // Add element to DOM
            this.HelpPopUp.parentNode.appendChild(this.Background);
            this.BackgroundAdded = true;
        }
    	
	    // Determine height and width of background div element
	    var clientWidth = this.getClientWidth();
	    var clientHeight = this.getClientHeight();
    	
	    // Update background element size
	    this.Background.style.width = Math.max(Math.max(document.documentElement.scrollWidth, document.body.scrollWidth), clientWidth)+'px';
	    this.Background.style.height = Math.max(Math.max(document.documentElement.scrollHeight, document.body.scrollHeight), clientHeight)+'px';
	    this.Background.style.display = 'block';
	}
	
    // Display pop up
    this.HelpPopUp.style.opacity = 0; 
    this.HelpPopUp.style.MozOpacity = 0; 
    this.HelpPopUp.style.KhtmlOpacity = 0; 
    this.HelpPopUp.style.filter = 'alpha(opacity=0)'; 
	this.HelpPopUp.style.zIndex = '9999';
	this.HelpPopUp.style.position = 'absolute';
	this.HelpPopUp.style.display = 'block';
    
    // Work out position
    var xPos = 0;
    var yPos = 0;

    xPos = getAscendingLefts(this.AlignmentControl, this.InPopUp);
    yPos = getAscendingTops(this.AlignmentControl, this.InPopUp);
    
    this.HelpPopUp.style.top = (yPos + this.OffsetY) + 'px';
    this.HelpPopUp.style.left = (xPos + this.OffsetX) + 'px';
	
	if (this.scrollRequired())
	{
	    if (this.ShowCloseOnScroll == true)
	    {
	        if (this.ClosePopUp)
	            // Show close link
	            this.ClosePopUp.style.display = 'block';
	    }
	    
	    // Re-position pop up
	    var newTop = parseInt(this.HelpPopUp.style.top.substr(0, (this.HelpPopUp.style.top.length - 2))) - parseInt(this.HeightDiff) - 5;
	    this.HelpPopUp.style.top = newTop + 'px';
	    
	    // Reset variable
	    this.HeightDiff = 0;
	}
	
	// Hide selects overlapping pop up
    this.checkSelectOverlap();
    
	// Fade in pop up
	this.fadeInPopUp();
}

ShowPopUp.prototype.hideHelp = function()
{
	// Hide the help pop up
    this.HelpPopUp.style.opacity = 0; 
    this.HelpPopUp.style.MozOpacity = 0; 
    this.HelpPopUp.style.KhtmlOpacity = 0; 
    this.HelpPopUp.style.filter = 'alpha(opacity=0)'; 
    this.HelpPopUp.style.display = 'none';
    
    // Show all select controls
    this.showSelectControls();
    
    // Hide background if we have one
    if (this.Background)
        this.Background.style.display = 'none';
}

// Determine if the pop up will display all in view
ShowPopUp.prototype.scrollRequired = function()
{
    var screenHeight = 0;
    var scrollPos = new scrollPosition();
    
    if ( document.all )
       screenHeight = document.documentElement.offsetHeight;
    else
       screenHeight = window.innerHeight;
       
    var bottomPos = getAscendingTops(this.HelpPopUp, this.InPopUp);
      
    var bottomPos = parseInt(this.HelpPopUp.style.top.substr(0, (this.HelpPopUp.style.top.length - 2))) + parseInt(this.HelpPopUp.offsetHeight);
    var totalHeight = parseInt(scrollPos.scrollY) + parseInt(screenHeight);
    
    if ( bottomPos > totalHeight )
    {
        this.HeightDiff = parseInt(bottomPos) - parseInt(totalHeight);
        return true;
    }
    else
        return false;
}

// Check if the pop up control will overlap any select elements & hide them
ShowPopUp.prototype.checkSelectOverlap = function()
{
	this.HiddenSelectControls = new Array();
    var selectControls = new Array();
    selectControls = document.getElementsByTagName('select');
    
    var popUpxPos = getAscendingLefts(this.HelpPopUp, this.InPopUp);
    var popUpyPos = getAscendingTops(this.HelpPopUp, this.InPopUp);

    for ( var x = 0; x < selectControls.length; x++ ) 
    {
        var selectControl = selectControls[x];
        
        var selectxPos = getAscendingLefts(selectControl, this.InPopUp);
		var selectyPos = getAscendingTops(selectControl, this.InPopUp);
		
		var selectxPosMax = selectxPos + selectControl.offsetWidth;
		var selectyPosMax = selectyPos + selectControl.offsetHeight;
        
        // Work out if select control sits within the dimensions of the pop up and hide if it does
        if ( (selectxPos >= popUpxPos && selectxPos <= (popUpxPos + this.HelpPopUp.offsetWidth)) ||
             (selectxPosMax >= popUpxPos && selectxPosMax >= (popUpxPos + this.HelpPopUp.offsetWidth)) ) 
        {
            if ( (selectyPos >= popUpyPos && selectyPos <= (popUpyPos + this.HelpPopUp.offsetHeight)) || 
                 (selectyPosMax >= popUpyPos && selectyPosMax <= (popUpyPos + this.HelpPopUp.offsetHeight)) ) 
            {
                selectControl.style.visibility = 'hidden';
                this.HiddenSelectControls[this.HiddenSelectControls.length] = selectControl;
            }
        }
    }
}

// Show any hidden select elements in the control array
ShowPopUp.prototype.showSelectControls = function()
{
    
	if (this.HiddenSelectControls != null && this.HiddenSelectControls.length != 0)
	{
		// Show all select controls as they may have been hidden
		for ( var x = 0; x < this.HiddenSelectControls.length; x++ ) {
			this.HiddenSelectControls[x].style.visibility = 'visible';
		}
		
		this.HiddenSelectControls.length = 0;
    }
    else
    {
		// Need to do this for when pop up is not closed using onmouseout
		var selects = new Array();
		selects = document.getElementsByTagName('SELECT');
		
		// Show all select controls as they may have been hidden
		for ( var x = 0; x < selects.length; x++ ) {
			selects[x].style.visibility = 'visible';
		}
    } 
}

ShowPopUp.prototype.getClientWidth = function()
{
	if (this.IsIE)
		return document.documentElement.clientWidth;
	else
		return Math.min(window.innerWidth, document.documentElement.clientWidth);
}

ShowPopUp.prototype.getClientHeight = function()
{
	if (this.IsIE)
		return document.documentElement.clientHeight;
	else
		return Math.min(window.innerHeight, document.documentElement.clientHeight);
}