Index: wp-includes/category-template.php
===================================================================
--- wp-includes/category-template.php	(revision 6148)
+++ wp-includes/category-template.php	(working copy)
@@ -334,7 +334,8 @@
 	global $wp_rewrite;
 	$defaults = array(
 		'smallest' => 8, 'largest' => 22, 'unit' => 'pt', 'number' => 45,
-		'format' => 'flat', 'orderby' => 'name', 'order' => 'ASC'
+		'format' => 'flat', 'orderby' => 'name', 'order' => 'ASC',
+		'useclass' => 0,
 	);
 	$args = wp_parse_args( $args, $defaults );
 	extract($args);
@@ -376,9 +377,18 @@
 		$tag_id = $tag_ids[$tag];
 		$tag_link = clean_url($tag_links[$tag]);
 		$tag = str_replace(' ', ' ', wp_specialchars( $tag ));
-		$a[] = "<a href='$tag_link' class='tag-link-$tag_id' title='" . attribute_escape( sprintf( __('%d topics'), $count ) ) . "'$rel style='font-size: " .
+		if (!useclass) {
+			$style = "style='font-size: " .
 			( $smallest + ( ( $count - $min_count ) * $font_step ) )
-			. "$unit;'>$tag</a>";
+			. "$unit;'";
+			$class ='';
+		} else {
+			$style ='';
+			$class =' tagcloud-'.( $smallest + ( ( $count - $min_count ) * $font_step ) );
+		}
+		$a[] = "<a href='$tag_link' class='tag-link-$tag_id$class' title='" . 
+			attribute_escape( sprintf( __('%d topics'), $count ) ) . 
+			"'$rel $style>$tag</a>";
 	}
 
 	switch ( $format ) :