WordPress MU

I'd like to limit the largest font size in the default Tag Cloud widget, and it looks like the place to do that is in the 'largest' argument of the wp_generate_tag_cloud function around line 599 of wp-includes/categories-template.php

But it doesn't seem to work when I clear my cache and refresh the site. I've also gone into Dashboard->Appearance->Widgets and resaved the Tag Cloud widget for good measure.

Am I looking in the wrong place?

Thanks.

Modifying the core files is a bad plan because it makes upgrade difficult.

Try this tag cloud plugin
http://wpmudevorg.wordpress.com/project/featured-blog-tag-cloud-widget-and-shortcode

It lets you set font size, how many tags it shows, order alphabetically or by popularity, and even point to a different blog.

There's another better tag cloud widget out there in the WP plugin repo. Blanking on the name, but it has all kinds of extra tag cloud options.

Found this extremely easy.
Via FTP or however you can edit pages on your server navigate to:
/wp-includes/category_template.php

Open with your editor of choice.

Every "category_template.php" page will have a different number of lines depending on a number of factors, but for me it was on line 528.
Look for this code snippet:

function wp_tag_cloud( $args = '' ) {
	$defaults = array(
		'smallest' => 8, 'largest' => 22, 'unit' => 'pt', 'number' => 45,
		'format' => 'flat', 'separator' => "\n", 'orderby' => 'name', 'order' => 'ASC',
		'exclude' => '', 'include' => '', 'link' => 'view', 'taxonomy' => 'post_tag', 'echo' => true
	);

Where 'largest' => 22, change that number to whatever font size you desire.

There are a number of different arguments you can change there as well, but this worked for me.

Yes but each time you upgrade WPMU you'll lose that change.