How does an HTML specification differ from a web browser's implementation of the same?

Question

The main function of a browser is to present the web resource you choose, by requesting it from the server and displaying it in the browser window. The way the browser interprets and displays HTML files is specified in the HTML and CSS specifications. The two biggest differences between web browsers are support and rendering. Which is the cause of differing from a web browser's implementation or something else?

Answer 1

An HTML specification, like the HTML5 specification, defines a set of rules that all documents need to strictly follow in order to be considered valid as per the specification. The specification also offers instructions about how a web browser must interpret and render a valid document. A web browser is considered to support a specification if it is able to handle valid documents as per the rules mentioned in the specification. Although all of the major browsers support most of the HTML5 specification, no web browser supports the HTML5 specification to its entirety.

Hence, it is all-important for the developers to confirm that the aspects of the specification that they are using must be supported by all the web browsers on which they want to display/deliver the content. As such, despite the improved specifications for HTML5, cross-browser support is still something that a developer should be very cautious about. The HTML5 specification defines certain rules that must be followed when coming across an invalid HTML5 document. Since invalid documents can contain anything, it is almost impossible for the HTML5 specification to handle all the possibilities comprehensively. Therefore, most decisions about handling malformed documents are entirely up to the web browser.

Answer 2

Html deals with how text, boxes, etc appear on the page. Implementation is something broader