The W3C is short for the World Wide Web Consortium. They are an international consortium where member organizations, a full time staff, and the public work together to develop web standards.

Tim Berners-Lee, W3C Director and inventor of the World Wide Web in 1989, created (with others) the W3C. Essentially, W3C ensures the web will be accommodating to the growing diversity of people, hardware, and software.

The W3C offers a validator at where you can enter in your web pages, upload your web page, or enter the source code directly.

The validator will site errors and warnings and give you a detailed description of the error. In short, this is like spell check for your code. It checks the spelling, grammar and syntax of your web pages unseen programming.

Browsers have error correction built in to correct some of the bad code you may have, but what one browser corrects in one way, another browser will correct differently (or not at all). What you see is not what others get.

Another point, if you have bad code in the back, the search engines won’t be able to read your site probably. So when people perform a search, either your page hasn’t been indexed, or it won’t display correctly.

Finally, consider people with disabilities who use screen readers. These readers read the programming code, which in turn reads it back to the user or increases the font. If you have bad coding, it can create an endless loop of errors. Thus making your website inaccessible.