// Source this file from each of the four course home pages.
	// It provides rollover states for the session images
	
	// July 2003
	// michael underscore mccrary at wgbh.org
		
	 //server location
	 //allows all URL location in function call to be root relative
	var site_root = document.location.href.substr(0,document.location.href.indexOf('teachingmath/'));
	site_root += 'teachingmath/';
	
	var courseIndex = document.location.href.indexOf('grades');
	var course = document.location.href.substring(courseIndex, courseIndex + 9);

	var coursedir = /gradesk_2/i;

	if (coursedir.test(course)) {
		session = "c01";
	}
	
	else if (course == "grades3_5") {
		session = "c02";
	}
	
	else if (course == "grades6_8") {
		session = "c03";
	}
	
	else if (course == "grades9_1") {
		course = "grades9_12";
		session = "c04";
	}
	
	
	img1on = new Image();   
	img1on.src = site_root + course + "/images/" + session + "_hm_sess01_ovr.gif";  
	img2on = new Image(); 
	img2on.src = site_root + course + "/images/" + session + "_hm_sess02_ovr.gif";  
	img3on = new Image(); 
	img3on.src = site_root + course + "/images/" + session + "_hm_sess03_ovr.gif";  
	img4on = new Image(); 
	img4on.src = site_root + course + "/images/" + session + "_hm_sess04_ovr.gif";  
	img5on = new Image(); 
	img5on.src = site_root + course + "/images/" + session + "_hm_sess05_ovr.gif";  
	img6on = new Image(); 
	img6on.src = site_root + course + "/images/" + session + "_hm_sess06_ovr.gif";  
	img7on = new Image(); 
	img7on.src = site_root + course + "/images/" + session + "_hm_hdr_02_ovr.gif";  
	
	img1off = new Image();  
	img1off.src = site_root + course + "/images/" + session + "_hm_sess01_off.gif"; 
	img2off = new Image();
	img2off.src = site_root + course + "/images/" + session + "_hm_sess02_off.gif";  
	img3off = new Image();
	img3off.src = site_root + course + "/images/" + session + "_hm_sess03_off.gif";  
	img4off = new Image();
	img4off.src = site_root + course + "/images/" + session + "_hm_sess04_off.gif";  
	img5off = new Image();
	img5off.src = site_root + course + "/images/" + session + "_hm_sess05_off.gif";  
	img6off = new Image();
	img6off.src = site_root + course + "/images/" + session + "_hm_sess06_off.gif"; 		
	img7off = new Image(); 
	img7off.src = site_root + course + "/images/" + session + "_hm_hdr_02.gif";  
	
	
	function imgOn(imgName) {
			if (document.images) {
				document[imgName].src = eval(imgName + "on.src");
			}
	}
	
	function imgOff(imgName) {
			if (document.images) {
				document[imgName].src = eval(imgName + "off.src");
			}
	}