function emailvalidation(entered, alertbox) {
with (entered){
apos=value.indexOf("@"); 
dotpos=value.lastIndexOf(".");
lastpos=value.length-1;
if (apos<1 || dotpos-apos<2 || lastpos-dotpos>4 || lastpos-dotpos<2) 
{if (alertbox) {alert(alertbox);} return false;}
else {return true;}}}

function emptyvalidation(entered, alertbox)
{
with (entered)
{
str = value.replace(/^\s*|\s*$/g,"");
if (str==null || str=="")
{if (alertbox!="") {alert(alertbox);} return false;}
else {return true;}}}

function valuevalidation(entered, min, max, alertbox, datatype)
{
with (entered)
{
checkvalue=parseFloat(value);
if (datatype)
{smalldatatype=datatype.toLowerCase();
if (smalldatatype.charAt(0)=="i") {checkvalue=parseInt(value)};
}
if ((parseFloat(min)==min && checkvalue<min) || (parseFloat(max)==max && checkvalue>max) || value!=checkvalue)
{if (alertbox!="") {alert(alertbox);} return false;}
else {return true;}}} 

function digitvalidation(entered, min, max, alertbox, datatype)
{
// Digit Validation by Henrik Petersen / NetKontoret
// Explained at www.echoecho.com/jsforms.htm
// Please do not remove this line and the two lines above.
with (entered)
{
checkvalue=parseFloat(value);
if (datatype)
{smalldatatype=datatype.toLowerCase();
if (smalldatatype.charAt(0)=="i") 
{checkvalue=parseInt(value); if (value.indexOf(".")!=-1) {checkvalue=checkvalue+1}};
}
if ((parseFloat(min)==min && value.length<min) || (parseFloat(max)==max && value.length>max) || value!=checkvalue)
{if (alertbox!="") {alert(alertbox);} return false;}
else {return true;}}} 

<!-- Begin Postcode Validate
function postcodevalidation(entered, alertbox){

with (entered)
{
 test = value; size = value.length;
 test = test.toUpperCase(); //Change to uppercase
  
 while (test.slice(0,1) == " ") //Strip leading spaces
  {test = test.substr(1,size-1);size = test.length;
  }
 while(test.slice(size-1,size)== " ") //Strip trailing spaces
  {test = test.substr(0,size-1);size = test.length;
  }

 value = test; //write back to form field

 if (size < 6 || size > 8){ //Code length rule
  alert(test + " is not a valid postcode - wrong length");
  return false;
  }
 if (!(isNaN(test.charAt(0)))){ //leftmost character must be alpha character rule
   alert(test + " is not a valid postcode - cannot start with a number");
   return false;
  }
 if (isNaN(test.charAt(size-3))){ //first character of inward code must be numeric rule
   alert(test + " is not a valid postcode - alpha character in wrong position");
   return false;
  }
 if (!(isNaN(test.charAt(size-2)))){ //second character of inward code must be alpha rule
   alert(test + " is not a valid postcode - number in wrong position");
   return false;
  }
 if (!(isNaN(test.charAt(size-1)))){ //third character of inward code must be alpha rule
   alert(test + " is not a valid postcode - number in wrong position");
   return false;
  }
 if (!(test.charAt(size-4) == " ")){//space in position length-3 rule
   alert(test + " is not a valid postcode - no space or space in wrong position");
   return false;
   }
 count1 = test.indexOf(" ");count2 = test.lastIndexOf(" ");
 if (count1 != count2){//only one space rule
   alert(test + " is not a valid postcode - only one space allowed");
   return false;
  }

}
return true;
}
//  End Postcode Validate --> 

//Telephone Number validation function
function telephonevalidation (entered) {

with (entered) {
	//Test for a string
	if (value!=null && value!="") {

		for (i = 0;  i < value.length;  i++)
 		{
		    	ch = value.charAt(i);
			if(! own_instring(ch))
			{
			return false;
			}
		}
		return true;
	}
	return false;
}
}
//In string function to test for valid substring, accomodates JavaScripts lack of VBScripts InStr() function
function own_instring(c)
{
	var checkOK = "0123456789-+-. ()\t\r\n\f";
	var ret  = false;
  	for (j = 0;  j < checkOK.length;  j++) {
      		if (c != checkOK.charAt(j)) {
			continue;
		} else {
			ret = true;
			break;
		}
	}
	return ret;
}