Note's style is implemented as the __style.html file (mandatory) and the __style subdirectory (optional); both located in the note's directory.

__style.html file is an HTML file encoded in UTF-8. The file is not supposed to be created or edited by user, rather by special macro which adds formatting tags as well as some additional parameters (see below) to the note content. Here is how the default style looks like:
<html>
<head>
	<meta http-equiv='content-type' content='text/html; charset=utf-8'/>

	<style type="text/css">
		body, div, p, table {
			font-size:${fontsize}pt;
			font-family:$fontfamily;
		}

		img{border:none}
		$userstyle
	</style>
	$userhead
</head>

<body>
<p>$content</p>
</body>
</html>

__style.html file contains references to macros that begin with "$" character followed by the macro name (it can be enclosed by braces), for example, $content or ${content}. The braces are used in case the macro name is not separated by space character from alphanumeric characters to follow. Currently, OutWiker's styles support the following macros:
__style directory is not mandatory. It can store images and files with CSS styles, if any. However, storing CSS styles in this directory is not encouraged, preferable solution is to incorporate them in the file __style.html. This is primarily due to the caching of styles when running under Linux. If several styles include CSS files of same name, then switching between those CSS may cause delays in rendering. There is no such problem if CSS is included directly into HTML code.