In general, HTML tags in the main content area of a site should be used without additional classes or in-line CSS styling. This provides consistent styling across an entire site. Differences in styling of the same HTML elements in different parts of the site should be provided by CSS selectors that start with structural elements of the region being targeted (usually <div> tags).
Never choose an HTML tag based on how it looks, as this may confuse screen readers for the blind, and may also decrease the relevance ranking of your content to web search engines.
The main website for the library uses HTML 5, and this is the recommended version of HTML to use for new sites. However, new semantic/structural elements in the HTML 5 standard, should be used with caution and tested extensively on older browsers. Other elements (for media, the <canvas>, form elements, and new input types) should probably be avoided. Most new structural elements (<article>, <header>, <footer>, <section>, etc.) are not styled in our base theme, and should be considered the same as the <div> tag for layout purposes.
Paragraphs vs. Divisions