One of the most important features of a good website is not directly visible to the end-user. A clear, detailed style guide is the key to a professional, readable site.

Your style guide should cover the following areas:

1. Fonts/Typesetting
2. Colours
3. Images
4. Content length
5. Advertisements (if applicable)
6. Banners (if applicable)
7. Page structure
8. Sitemap conventions

An example font style guide would read as follows:

Headings
Headings use the Verdana font, with a size of 17px, and a line height of 23px. Text is bold, and black (unless also a link). Headings are aligned to the left.

Body Text
Body text is Verdana, with a size of 12px, and a line height of 16px. Body text, excepting links, is black. Body text is left-justified.

Links, Lists & Blockquotes
Links, lists, blockquotes and similar common content types should be automatically styled using the site stylesheet. For example, every link will automatically appear blue with an underline, and every bullet list will automatically use square bullets.

Note that some of the above style guide (eg. line heights) should also be hard coded into the site itself. The guide should still include these, however, in case a site administrator overrides the correct settings.

While the use of a style guide can seem limiting, it ensures that your content is communicated effectively, by making the most of the professional design and layout you have purchased. In essence, it means that your site is being used correctly, and should more fully realise its intended purpose.