Website Coding Errors (W3C Standards)
HTML (Hyper Text Markup Language) is the language that web pages are finally published in, regardless of the code that is used to generate them.
The World Wide Web Consortium (W3C) was founded by, amongst other, Sir Tim Berners-Lee, the inventor of the Internet, in 1994. By 1999, the first agreed set of coding standards was published by W3C. In layman's terms, these laid out the coding standards that, if adhered to, would lead to websites displaying correctly on more devices, screen sizes and browsers and with fewer errors. Almost like building regs for websites, if you like.
Any web page could be tested against these standards and, the fewer the number of coding errors and coding warnings, the more robust the web page would be and the more confident you would be that the website would perform well for everyone, regardless of the browser used.
W3C is chiefly concerned with Coding Standards and is separate from the WCAG Guidelines, which are only concerned with website accessibility. There were times at which the first releases of each would contradict each other, although we have seen a more harmonic relationship develop over recent years.
WCAG 2.0 was first published in 2008 and WCAG 2.1 was published in 2018. This is the latest set of standards. WCAG 3.0 is in development but is some years off.
Although not directly concerned with Accessibility, Coding Standards are still an Accessibility issue, anything that could affect the functioning of a website for a user is an accessibility issue, as that person may be disabled.
This metric is one of many used by Google in determining the build quality of a website and is a significant ranking factor. Everything is relative with Google, the larger the number of errors, the more significantly its position in search engines' listings will be affected.
There are some websites that we have reviewed that contained over 500 errors on the Home page alone. The record was 981 coding errors.