function ajaxFunction(url, returnfunction)
{
	var xmlhttp;
	if (window.XMLHttpRequest)
		xmlhttp = new XMLHttpRequest();
	else if (window.ActiveXObject)
		xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
	else
		alert("Your browser is not compatible with this website. Please update your browser or contact us for technical support.");
	xmlhttp.onreadystatechange = returnfunction;
	xmlhttp.open("GET", url ,true);
	xmlhttp.send(null);
}

/* form validation functions */

function validate_fieldisstring(fieldname)
{
	var str = document.getElementById(fieldname).value;
	return str.length > 0 ? false : true
}

function validate_fieldisemail(fieldname)
{
	var email = trim(document.getElementById(fieldname).value);
	var RegExp = /^((([a-z]|[A-Z]|[0-9]|!|#|$|%|&|'|\*|\+|\-|\/|=|\?|\^|_|`|\{|\||\}|~)+(\.([a-z]|[0-9]|!|#|$|%|&|'|\*|\+|\-|\/|=|\?|\^|_|`|\{|\||\}|~)+)*)@((((([a-z]|[0-9])([a-z]|[0-9]|\-){0,61}([a-z]|[0-9])\.))*([a-z]|[0-9])([a-z]|[0-9]|\-){0,61}([a-z]|[0-9])\.)[\w]{2,4}|(((([0-9]){1,3}\.){3}([0-9]){1,3}))|(\[((([0-9]){1,3}\.){3}([0-9]){1,3})\])))$/
	if(RegExp.test(email))
		return false
	else
		return true
}
function validate_password(fieldname)
{
	var strng = document.getElementById(fieldname).value;
	var error = "";
	if (strng == "")
		error = "You didn't enter a password."
	var illegalChars = /[\W_]/
	if (strng.length < 6)
		error = "Your password must be at least 6 characters long"
	else if (illegalChars.test(strng))
		error = "Your password must not contain any non-alphanumeric characters"
	return error
}
function validate_checkboxischecked(id)
{
	var ischecked = document.getElementById(id).checked 
	return ischecked ? false : true
}

function validate_range(id, minvalue, maxvalue)
{
	var inputobj = parseFloat(document.getElementById(id).value);
	return ((minvalue != "" && inputobj < minvalue) || (maxvalue != "" && inputobj > maxvalue));
}

function OpenLink(strUrl)
{
	var left = parseInt((screen.availWidth / 2) - (990 / 2));
    var top = parseInt((screen.availHeight / 2) - (750 / 2));
	window.open(strUrl, "ebook", "status=0,toolbar=0,location=0,menubar=0,directories=0,resizable=1,scrollbars=1,height=750,width=990,left=" + left + ",top=" + top );
}

function trim(str, chars) {
	return ltrim(rtrim(str, chars), chars);
}

function ltrim(str, chars) {
	chars = chars || "\\s";
	return str.replace(new RegExp("^[" + chars + "]+", "g"), "");
}

function rtrim(str, chars) {
	chars = chars || "\\s";
	return str.replace(new RegExp("[" + chars + "]+$", "g"), "");
}