function MM_validateForm() { //v4.0
  var i,p,q,nm,test,num,min,max,errors='',args=MM_validateForm.arguments;
  for (i=0; i<(args.length-2); i+=3) { test=args[i+2]; val=MM_findObj(args[i]);
    if (val) { nm=val.name; if ((val=val.value)!="") {
      if (test.indexOf('isEmail')!=-1) { p=val.indexOf('@');
        if (p<1 || p==(val.length-1)) errors+='- '+nm+' must contain an e-mail address.\n';
      } else if (test!='R') { num = parseFloat(val);
        if (isNaN(val)) errors+='- '+nm+' must contain a number.\n';
        if (test.indexOf('inRange') != -1) { p=test.indexOf(':');
          min=test.substring(8,p); max=test.substring(p+1);
          if (num<min || max<num) errors+='- '+nm+' must contain a number between '+min+' and '+max+'.\n';
    } } } else if (test.charAt(0) == 'R') errors += '- '+nm+' is required.\n'; }
  } if (errors) alert('The following error(s) occurred:\n'+errors);
  document.MM_returnValue = (errors == '');
}

<!-- newsletter subscribe below here --> 
var fieldstocheck = new Array(); 
fieldnames = new Array(); 
function checkform() { 
for (i=0;i<fieldstocheck.length;i++) { 
if (eval("document.subscribeform.elements['"+fieldstocheck[i]+"'].value") == "") { 
alert("Please enter your "+fieldnames[i]); 
eval("document.subscribeform.elements['"+fieldstocheck[i]+"'].focus()"); 
return false; 
} 
} 
return true; 
} 
function addFieldToCheck(value,name) { 
fieldstocheck[fieldstocheck.length] = value; 
fieldnames[fieldnames.length] = name; 
}