Improve language string.

lang/en/tiny_htmlblock.php

@@ -38,7 +38,7 @@
 $string['labelhtml'] = 'HTML Code';
 $string['maxcatlevels'] = 'Category levels to show';
 $string['maxcatlevels_all'] = 'all';
-$string['maxcatlevels_desc'] = 'When defining HTML blocks below, in the category selector limit the options to some levels only, do not show all categories of any level.';
+$string['maxcatlevels_desc'] = 'When defining HTML blocks below, limit the options to some levels only in the category selector. Thus, the category selector does not show all categories of any level.';
 $string['menutext'] = 'HTML blocks';
 $string['pluginname'] = 'Tiny HTML Blocks';
 $string['settings'] = 'Predefine HTML Blocks for TinyMCE';