function validateEmpty(fld) 
{
    var error = "";
 
    if (fld.value.length == 0) 
    {
        fld.style.background = 'Yellow'; 
        error = "The required field has not been filled in.\n"
    } 
    else 
    {
        fld.style.background = 'White';
    }
    return error;  
}

function validateName(fld) 
{
    var error = "";
 
    if (fld.value.length == 0) 
    {
        fld.style.background = 'Yellow'; 
        error = "Please enter your name.\n"
    } 
    else 
    {
        fld.style.background = 'White';
    }
    return error;  
}

function validateAreaCode(fld)
{
    var re3digit=/^\d{3}$/ //regular expression defining a 3 digit number;
    var error = "";

    if (fld.value == "")
    {
        fld.style.background = 'Yellow';
        error = "Please enter your phone area code.\n"
        
    }

    else if (fld.value.search(re3digit)==-1) //if match failed
    {
        fld.style.background = 'Yellow';
        error = "Please enter a valid area code.\n";
    }
    else
    {
        fld.style.background = 'White';
    }
    return error; 
}

function validatePrefix(fld)
{
    var re3digit=/^\d{3}$/ //regular expression defining a 3 digit number;
    var error = "";

    if (fld.value == "")
    {
        fld.style.background = 'Yellow';
        error = "Please enter your phone prefix.\n"
        
    }

    else if (fld.value.search(re3digit)==-1) //if match failed
    {
        fld.style.background = 'Yellow';
        error = "Please enter a valid phone prefix.\n";
    }
    else
    {
        fld.style.background = 'White';
    }
    return error; 
}

function validateSuffix(fld)
{
    var re4digit=/^\d{4}$/ //regular expression defining a 4 digit number;
    var error = "";

    if (fld.value == "")
    {
        fld.style.background = 'Yellow';
        error = "Please enter your phone suffix.\n"
        
    }

    else if (fld.value.search(re4digit)==-1) //if match failed
    {
        fld.style.background = 'Yellow';
        error = "Please enter a valid phone suffix.\n";
    }
    else
    {
        fld.style.background = 'White';
    }
    return error; 
}

function trim(s)
{
  return s.replace(/^\s+|\s+$/, '');
}

function validateEmail(fld) 
{
    var error="";
    var tfld = trim(fld.value);                        // value of field with whitespace trimmed off
    var emailFilter = /^[^@]+@[^@.]+\.[^@]*\w\w$/ ;
    var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/ ;
   
    if (fld.value == "") 
    {
        fld.style.background = 'Yellow';
        error = "Please enter your email address.\n";
    } 
    else if (!emailFilter.test(tfld)) 
    {              //test email for illegal characters
        fld.style.background = 'Yellow';
        error = "Please enter a valid email address.\n";
    } 
    else if (fld.value.match(illegalChars)) 
    {
        fld.style.background = 'Yellow';
        error = "The email address contains illegal characters.\n";
    } 
    else 
    {
        fld.style.background = 'White';
    }
    return error;
}

function validateMessage(fld) 
{
    var error = "";
 
    if (fld.value.length == 0) 
    {
        fld.style.background = 'Yellow'; 
        error = "Please enter a message.\n"
    } 
    else 
    {
        fld.style.background = 'White';
    }
    return error;  
}
function validateForm(form) 
{
    var reason = "";
    reason += validateName(form.name);
    reason += validateAreaCode(form.areaCode);
    reason += validatePrefix(form.prefix);
    reason += validateSuffix(form.suffix);
    reason += validateEmail(form.email);
    reason += validateMessage(form.comment);
   

    if (reason != "") 
    {
        alert("The following fields need attention:\n" + reason);
        return false;
    }

    return true;
}