function validRequired(formField,fieldLabel)
{
var result = true;
if (formField.value == "")
	{
	alert('Please enter a value for the "' + fieldLabel +'" field.');
	formField.focus();
	result = false;
	}
return result;
}

function validString(formField,fieldLabel,minLength,maxLength)
{
if ( formField.value.match(/[^a-z|^0-9|^_]/i) ) 
	{
	alert(fieldLabel + " must contain only letters and numbers.");
	formField.focus();
	return false;
	}
if (minLength > formField.value.length)
	{
	alert(fieldLabel + " must contain at least " + minLength +  " characters.");
	formField.focus();
	return false;
	}
if (maxLength < formField.value.length)
	{
	alert(fieldLabel + " may contain no more than " + maxLength +  " characters.");
	formField.focus();
	return false;
	}
return true;
}

function validateForm(theForm)
{
if (!validRequired(theForm.formusername,"user name")) 
	return false;
if (!validString(theForm.formusername,"user name",4,20)) 
	return false;
if (!validRequired(theForm.formpassword,"password")) 
	return false;
if (!validString(theForm.formpassword,"password",3,20)) 
	return false;
return true;
}