Q What is the difference between HTML and XHTML?

Q What is sprintf.js?

Q What is the difference between XHTML 1.0 and XHTML 1.1 doctype declarations?

XHTML was developed to make HTML more extensible and flexible to work with other data formats (such as XML). In addition, browsers ignore errors in HTML pages, and try to display the website even if it has some errors in the markup. So XHTML comes with a much stricter error handling.

sprintf.js is a JavaScript library that provides a way to format strings using a syntax similar to the sprintf function in C and other languages. sprintf.js isn't specifically designed for number calculations, but rather for formatting strings. However, it can be quite useful when one needs to format the output of one's calculations in a specific way.

When authoring document is HTML or XHTML, it's important to add a doctype declaration to be sure the document will be parsed the same way by different browsers. Unlike XML 1.0, XML 1.1 is forward compatible with the Unicode Standard. The XML 1.1 processor is able to process documents that use characters that will be allotted in future versions of the Unicode Standard, which will presumably contain additional language characters.