myImages=new Array();
myImages[0]="_images/AD.jpg";
myImages[1]="_images/nav_breast.jpg";
myImages[2]="_images/nav_face.jpg";
myImages[3]="_images/nav_abdomen.jpg";
var imagecounter=myImages.length-1
var i = 0;

// Show an image based on its number //
function show_image(number,ident)
{ if ( (number <= imagecounter) || (number >=0 ) )
	{ document.getElementById(ident).src=myImages[number]; }
}

// show an image based on its position //
function first(ident)
{ document.getElementById(ident).src=myImages[0]
	i=0;
}

function previous(ident)
{ if (i>0)
	{ i--;
		document.getElementById(ident).src=myImages[i];
	}
}

function next(ident)
{ if (i<imagecounter)
	{ i++;
		document.getElementById(ident).src=myImages[i];
	}
}

function last(ident)
{ document.getElementById(ident).src=myImages[imagecounter];
	i=imagecounter;
}

// toogle a textbox visibility and display on and off //
function show_hide(text_box)
{
  var visibility = document.getElementById(text_box).style.visibility
	if (visibility=="visible")
	{ 
	  	document.getElementById(text_box).style.visibility="hidden";
			document.getElementById(text_box).style.display="none";
	} 
	else
	{ 
			document.getElementById(text_box).style.visibility="visible";
			document.getElementById(text_box).style.display="block";
	}
	return true;
}

function hide(text_box)
{
	document.getElementById(text_box).style.visibility="hidden";
	document.getElementById(text_box).style.display="none";
	return true;
}

<!-- change a box background color on mouse action -->
function change_background(id,color)
{ 
	document.getElementById(id).style.background=color;
}

function Start(page) 
{
OpenWin = this.open(page, "CtrlWindow",  "toolbar=no,menubar=no,location=no,scrollbars=yes,resizable=yes,width=600,height=800,left=150,top=30");
}