$relative_template_dir

behaves almost like $template_dir, except that it adds an extra feature of a relative path when it traverses on deep directories.

Sample Usage: (e.g. head.tpl)

<link href="{$relative_template_dir}style.css" rel="stylesheet" type="text/css" >

HTML Source Output

Sample #1:  Documentation Section
Site Path: /Documentation/

<link href="../_templates/main/style.css" rel="stylesheet" type="text/css">

Sample #2:  Web Designer Section
Site Path: /Documentation/Web.Designer/

<link href="../../_templates/main/style.css" rel="stylesheet" type="text/css">