<isindex> is an obsolete HTML element that puts a text field in a page for querying the document.<isindex> was providing a single line text input for entering a query string. When sent, the server would return a list of pages matching the query. It supports depended on both the browser and the server to react to the query.
<nextid> is an obsolete HTML element that served to enable the NeXT web designing tool to generate automatic NAME labels for its anchors. It was generated by that web editing tool automatically and was not to be adjusted or entered by hand. This element has the distinction of being the first element to become one of the "Lost Tags" by being eliminated from the official public DTD's of the HTML versions. It is also probably one of the least understood of all of the early HTML elements.
The <noembed> element is a deprecated and non-standard way to provide alternative, or "fallback", content for browsers that do not support the <embed> element or do not support embedded content an author wishes to use. This element was deprecated in HTML 4.01 and above in favor of <object>. Fallback content should be inserted between the opening and closing <object> tags.
The getYear() method returns the year in the specified date according to local time. Because getYear() does not return full years ("year 2000 problem"), it is no longer used and has been replaced by the getFullYear() method.
The setYear() method sets the year for a specified date according to local time. Because setYear() does not set full years ("year 2000 problem"), it is no longer used and has been replaced by the setFullYear() method.
The toGMTString() method converts a date to a string, using Internet Greenwich Mean Time (GMT) conventions. The exact format of the value returned by toGMTString() varies according to the platform and browser, in general it should represent a human readable date string.
The __proto__ property of Object.prototype is an accessor property (a getter function and a setter function) that exposes the internal [[Prototype]] (either an object or null) of the object through which it is accessed.