Answer Wiki. An MRI is a series of detailed picture of your brain, as they were at the time the MRI was done. They are valid as long as no other changes occur. Basically, if somebody has an MRI today that is normal, and have a stroke or hernia tomorrow, obviously the result will change (You never know).
Web browser. A web browser (commonly referred to as a browser) is a software application for retrieving, presenting and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI/URL) that may be a web page, image, video or other piece of content.
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.