function checkForm() {
    if ( document.getElementById( 'username' ).value.length < 3 ) {
        alert( 'Please enter your username' );
        document.getElementById( 'username' ).focus();
        return false;
    } else if ( document.getElementById( 'tel' ).value.length < 5 ) {
        alert( 'Please enter your telephone number' );
        document.getElementById( 'tel' ).focus();
        return false;
    } else if ( document.getElementById( 'email' ).value.length < 5 ) {
        alert( 'Please enter your email address' );
        document.getElementById( 'email' ).focus();
        return false;
    } else if ( document.getElementById( 'telephone' ).value.length < 5 ) {
        alert( 'Please enter your phone number' );
        document.getElementById( 'telephone' ).focus();
        return false;
    } else if ( document.getElementById( 'enquiry' ).value.length < 5 ) {
        alert( 'Please enter your enquiry' );
        document.getElementById( 'enquiry' ).focus();
        return false;
    }
    return true;
}