Clean, Error-free Codes
While this is not the primary rule in search engine optimization, it surely does pay to make your website W3C compliant. For one, it enhances user accessibility. Clean and error-free codes make your website load faster and compatible to multiple browsers. The overall user experience is thus greatly improved.
Cleaning up also reduces the amount of code making it easier for search engine bots to crawl your site. Hence in effect, the advantage of having logically structured, error-free code is two-fold. It improves SEO and as well as enhances user experience. We should remember it is user optimization that helps convert the traffic brought in through SEO efforts.
Cascading Style Sheets
Another factor that reduces file size and quickens the loading of web pages is the use of CSS. Cascading style sheet is a file that defines and controls various presentation characteristics on a web page. It allows the separation of web page content from its stylistic elements such as layout, color, font size etc. This separation reduces the complexity of a web page and makes it load faster.
Using an external CSS gives you more flexibility and control over the formatting elements when used for multiple pages. Implementing and maintaining modifications become much more easier as it is externally located rather than on individual pages.
Search engines use the top-down approach when they crawl a website. This implies that whatever is at the very top of your source page gets crawled first and sometimes crawlers stop reading a page before reaching its end. Hence from an SEO perspective, it is best to have your content as near the top as possible. Applying CSS makes this possible. CSS takes out the chunk of your styling codes moving the content further up on a page. Search engines therefore get a chance to see much more of the page content and this could improve the site’s rank on the SERP.