Sinoatrial node. The sinoatrial node (SAN; also known as sinus node) is a group of cells located in the wall of the right atrium of the heart.
How Do Web Browsers Work? The World Wide Web is a system of Internet servers that support specially formatted documents. Web browsers are used to make it easy to access the World Wide Web. Browsers are able to display Web pages largely in part to an underlying Web protocol called HyperText Transfer Protocol (HTTP).
A browser extension is a plug-in that extends the functionality of a web browser. Some extensions are authored using web technologies such as HTML, JavaScript, and CSS. Others are developed using machine code and application programming interfaces provided by web browsers, such as NPAPI and PPAPI. Browser extensions can change the user interface of the web browser without directly affecting viewable content of a web page; for example, by adding a browser toolbar.