xls The .xls filename extension is a native binary file format associated with the closed source spreadsheet application Microsoft Office Excel. First introduced in 1987 with the release of Excel 2.x, the file format acts as the container for storing spreadsheet data such as work sheets, charts, and macros. Prior to Microsoft Office Excel 2007, the xls binary format was the default standard for the Microsoft Office Excel until the later adoption of the Open Document standard .xlsx. Documents to be saved in the .xls format are saved as Excel 97, 2003 documents.
html The hypertext markup language, commonly referred to as HTML is at the backbone of the internet and World Wide Web. It is the standard markup language used in the creation of webpages and was released in 1993 at the advent of the internet. The format defines the structure and layout of a webpage through markup tags such as header tags and image tags from which a browser can interpret multimedia information for on screen presentation. To view files and webpages saved with the .html filename extension, one needs a compatible web browser that implements the HTML specification. Because the format is open source, several browsers which are mostly free to use can open such files. The World Wide Web consortium actively maintains and updates the html specification.