Cascading style sheets are external files that control various type and formatting attributes of elements on a web page. Some people include all of the font, table, and color-type formatting right inside the web page, which can add hundreds of lines of extraneous code, which dilutes keyword emphasis and slows down page load times. Moving all of the formatting attributes to an external .css file can also speed up load times and make your website much more search-friendly. Site errors may include broken links, indexed 404 pages or errors in sitemap files to name a few. On the other hand, they will be missing for search engines. Mobile content should be short, useful, interesting, and easy to navigate.