function checkform(of)
{
// Test if DOM is available and there is an element called required
if(!document.getElementById || !document.createTextNode){return;}
if(!document.getElementById('required')){return;}

// Define error messages and split the required fields
var errorID='errormsg';
var errorClass='error'
var errorMsg='Please fill in the fields marked with ';
var errorImg='images/x1.gif';
var errorAlt='Error';
var errorTitle='This field has an error!';
var reqfields=document.getElementById('required').value.split(',');

// Cleanup old mess
// if there is an old errormessage field, delete it
if(document.getElementById(errorID))
{
var em=document.getElementById(errorID);
em.parentNode.removeChild(em);
			}
// remove old images and classes from the required fields
for(var i=0;i<reqfields.length;i++)
{
var f=document.getElementById(reqfields[i]);
if(!f){continue;}
if(f.previousSibling && /img/i.test(f.previousSibling.nodeName))
{
f.parentNode.removeChild(f.previousSibling);
}
f.className='';
}
// loop over required fields
for(var i=0;i<reqfields.length;i++)
{
// check if required field is there
var f=document.getElementById(reqfields[i]);
if(!f){continue;}
// test if the required field has an error, 
// according to its type
switch(f.type.toLowerCase())
{
case 'text':
if(f.value=='' && f.id!='email'){cf_adderr(f)}							
// email is a special field and needs checking
if(f.id=='email' && !cf_isEmailAddr(f.value)){cf_adderr(f)}							
break;
case 'textarea':
if(f.value==''){cf_adderr(f)}							
break;
case 'checkbox':
if(!f.checked){cf_adderr(f)}							
break;
case 'select-one':
if(!f.selectedIndex && f.selectedIndex==0){cf_adderr(f)}							
break;
}
}
return !document.getElementById(errorID);

/* Tool methods */
function cf_adderr(o)
{
// create image, add to and colourise the error fields
var errorIndicator=document.createElement('img');
errorIndicator.alt=errorAlt;
errorIndicator.src=errorImg;
errorIndicator.title=errorTitle;
o.className=errorClass;
o.parentNode.insertBefore(errorIndicator,o);

// Check if there is no error message
if(!document.getElementById(errorID))
{
// create errormessage and insert before submit button
var em=document.createElement('div');
em.id=errorID;
var newp=document.createElement('p');
newp.appendChild(document.createTextNode(errorMsg))
// clone and insert the error image
newp.appendChild(errorIndicator.cloneNode(true));
em.appendChild(newp);
// find the submit button 
for(var i=0;i<of.getElementsByTagName('input').length;i++)
{
if(/submit/i.test(of.getElementsByTagName('input')[i].type))
{
var sb=of.getElementsByTagName('input')[i];
break;
}
}
if(sb)
{
sb.parentNode.insertBefore(em,sb);
}	
} 
}
function cf_isEmailAddr(str) 
{
return str.match(/^[\w-]+(\.[\w-]+)*@([\w-]+\.)+[a-zA-Z]{2,7}$/);
}
}