CSS (Cascading Style Sheets)
Cascading Style-Sheets, otherwise know as CSS are used to style un-styled HTML. This developers to separate the code from the design. In turn, this also makes it easier to make style updates that impact a variety of pages or page templates at once, without having to re-code every page. CSS are great, and can help improve load time for a site, but over time, they are often added and updated many times without being trimmed, pruned or audited; this can cause the opposite impact. It is best to use only the styles that you need, remove unused ‘style classes’ in the style sheets, and don’t link to style-sheets that are not needed to render a page. In an ideal situation, a site would have one global style sheet, and one style sheet for each page template, and that is it. Adding multiple style sheets to pages can slow down the load time of the page, especially on mobile devices. In some cases, loading style sheets too slowly or without place-holders in the template can cause the page to appear to wiggle or flash once or twice, as the styles are applied. This is often referred to as ‘jank’.