function validate_form()
{
    valid = true;

    if ( document.contactus.name.value == "" )
    {
        alert ( "Please fill in the 'Your name' box." );
        valid = false;
    }
    
    if ( document.contactus.company.value == "" )
    {
        alert ( "Please fill in the 'Company' box." );
        valid = false;
    }

    if ( document.contactus.email.value == "" )
    {
        alert ( "Please fill in the 'Email' box." );
        valid = false;
    }

    if ( document.contactus.message.value == "" )
    {
        alert ( "Please fill in the 'Message' box." );
        valid = false;
    }
    return valid;
}