function checkEmail (strng) 
{
	var error="";
	if (strng == "") 
	{
		error = "You didn't enter an email address.\n";
	}
	
	var emailFilter=/^.+@.+\..{2,3}$/;
	if (!(emailFilter.test(strng))) 
	{ 
		error = "Please enter a valid email address.\n";
	}
	else 
	{
		//test email for illegal characters
		var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/
		if (strng.match(illegalChars)) 
		{
			error = "The email address contains illegal characters.\n";
		}
	}
	return error;    
}

// phone number - strip out delimiters and check for 10 digits
function checkPhone (strng) 
{
	var error = "";
	if (strng == "") 
	{
		error = "You didn't enter a phone number.\n";
	}
	
	var stripped = strng.replace(/[\(\)\.\-\ ]/g, ''); //strip out acceptable non-numeric characters
	if (isNaN(parseInt(stripped))) 
	{
		error = "The phone number contains illegal characters.";
	
	}
	if (!(stripped.length == 10)) 
	{
		error = "The phone number is the wrong length. Make sure you included an area code.\n";
	} 
	return error;
}

// password - between 6-8 chars, uppercase, lowercase, and numeral
function checkPassword (strng) 
{
	var error = "";
	if (strng == "") 
	{
		error = "You didn't enter a password.\n";
	}
	
	var illegalChars = /[\W_]/; // allow only letters and numbers
	
	if (illegalChars.test(strng)) 
	{
		error = "The password contains illegal characters, letters and numbers only.\n";
	} 
	if ((strng.length < 6) || (strng.length > 10)) 
	{
		error = "The password must be between 6 and 10 characters.\n";
	}
	return error;    
}    

// username - 4-10 chars, uc, lc, and underscore only.
function checkUsername (strng) 
{
	var error = "";
	if (strng == "") 
	{
		error = "You didn't enter a username.\n";
	}
	
	
	var illegalChars = /\W/; // allow letters, numbers, and underscores
	if ((strng.length < 4) || (strng.length > 10)) 
	{
		error = "The username must be between 4 and 10 characters.\n";
	}
	else if (illegalChars.test(strng)) 
	{
		error = "The username contains illegal characters.\n";
	} 
	return error;
}       

// non-empty textbox
function isEmpty(strng) 
{
	var error = "";
	if (strng.length == 0) 
	{
		error = "The mandatory text area has not been filled in.\n"
	}
	return error;	  
}

// was textbox altered
function isDifferent(strng) 
{
	var error = ""; 
	if (strng != "Can\'t touch this!") 
	{
		error = "You altered the inviolate text area.\n";
	}
	return error;
}

// exactly one radio button is chosen
function checkRadio(checkvalue)
{
	var error = "";
	if (!(checkvalue)) 
	{
		error = "Please check a radio button.\n";
	}
	return error;
}

// valid selector from dropdown list
function checkDropdown(choice) 
{
	var error = "";
	if (choice == 0) 
	{
		error = "You didn't choose an option from the drop-down list.\n";
	}    
	return error;
}