Showing “0” pageview when there is no view

You can optimize your code a bit and localize it. I would add the results from get_post_meta() to a variable and then check the returned result an act upon that

You can try something like this

<div class="mypageview">
    <?php 
        $views = get_post_meta( $post->ID, 'pageview', true );
        if ( !$views ) 
            _e( '0 post views' );

        if ( $views == 1 )
            _e( '1 post view' );

        if ( $views > 1 )
            printf(__( ' %s post views' ), $views);
    ?>
</div>

EDIT

On request in comments, you can rewrite the code to the following (I assume $output is defined previously before this code)

$output .= '<div class="mypageview">';
$views = get_post_meta( $post->ID, 'pageview', true );
if ( !$views ) 
$output .=  __( '0 post views' );

if ( $views == 1 )
$output .= __( '1 post view' );

if ( $views > 1 )
$output .= sprintf(__( ' %s post views' ), $views);
$output .= '</div>';