Add HTML to WordPress Widget Titles

add-html-to-wordpress-widget-titles.php

<?php
//allow html in widget title
function md_change_widget_title($title)
{
    //convert square brackets to angle brackets
    $title = str_replace('[', '<', $title);
    $title = str_replace(']', '>', $title);

    //strip tags other than the allowed set
    $title = strip_tags($title, '<a><blink><br><span>');
    return $title;
}
add_filter('widget_title', 'md_change_widget_title');
?>