missing meta title

Your header.php file should contain something like this:

}?>
<title><?php wp_title(”); ?></title>
</head>

Inbetween <title> and </title> you should have <?php wp_title(”); ?> and nothing else for the plugin to work corectly

<title>
<?php if(is_home() ) { bloginfo('name'); ?> | <?php bloginfo('description'); } ?>
<?php if(is_single() || is_page() || is_archive() || is_tag() || is_category() ) { wp_title('',true); ?> | <?php bloginfo('name'); } ?>
<?php if(is_404()) { ?> <?php _e('404 Error! Page Not Found','domain'); ?> | <?php bloginfo('name'); } ?>
<?php if(is_search()) { ?><?php _e('Search results for:','domain'); ?> <?php echo wp_specialchars($s, 1); ?> | <?php bloginfo('name'); } ?>
</title>