How can I have this?

If your site uses widgets, you can add a tag cloud. That would be pretty much the same thing.

What’s your website address? Do you have a sidebar? Just create a widget. Based on your website, I can tell you how.

Can’t open your site … if you have a sidebar, put this in your functions.php and register the widget:

[ Moderator Note: Please post code or markup snippets between backticks or use the code button. Don’t use blockquote, it ruins the formatting. ]

if ( function_exists('register_sidebar') ){
    register_sidebar(array(
        'name' => 'my_sidebar_widget',
        'before_widget' => '<div id="my-widget-area">',
        'after_widget' => '</div>',
        'before_title' => '',
        'after_title' => '',
));
}

Then put this in where you wanna place your widget area:

<?php /* Widgetized sidebar */
    if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('my_sidebar_widget') ) : ?><?php endif; ?>

Well, there are several ways to make tag clouds, and several online tools … including Tag Crowd, and several others that have different visual effects.

I, personally, would do whatever you could do without editing the core WP files. Too many people do that, then get all bent out of shape when they update their WP, and everything disappears.