Internet and Web

Cookies are small text files stored on a user's device that help websites recognize returning visitors and maintain session state. Plug-ins add functionality, scripts execute code, and ASPs are server-side technologies - none of these are used for user identification.

Correct answer is (3). 

E-mail (Electronic Mail) is a method of exchanging digital messages across computer networks. The term directly reflects its nature - mail delivered electronically rather than physically. It's one of the most fundamental and widely used applications on the internet.

Matt Cutts was a well-known software engineer at Google who famously maintained a popular personal blog focusing on search engine optimization and Google updates.

Among the given options, 'Network of computers' is the closest to describing WWW, though this is imprecise. WWW (World Wide Web) is a system of interlinked hypertext documents accessed over the internet. The options are poorly framed - WHO and 'UN organization' are irrelevant.

DIALOG is a classic online information retrieval service that provides access to databases and information services. It operates as an online service where users can search and retrieve information from various databases in real-time. The term 'online service' best describes its operational model.

The entity header in HTTP supplies information about the body of the document, such as its content length, type, and encoding. It can be present in both request and response messages that contain a body. General headers apply to both types, while request and response headers are specific to their respective message types.

Google was the world's most popular website in 2011, with billions of searches daily. As a search engine and web services giant, it dominated internet traffic and remained the most visited site globally for many years, far surpassing competitors like Yahoo, MSN, and AOL.

Address-to-name resolution (reverse DNS) uses the inverse domain (in-addr.arpa). This allows mapping IP addresses back to domain names, which is useful for verification and logging purposes.

HTTP is an application-layer protocol that shares characteristics with both FTP (File Transfer Protocol) and SMTP (Simple Mail Transfer Protocol). Like FTP, HTTP uses text-based commands and responses. Like SMTP, HTTP has a simple request-response model and uses headers for metadata exchange.

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) and may be a web page, image, video or other piece of content.

Metasearch engines (like Dogpile, Metacrawler) do not maintain their own database. Instead, they forward user queries to multiple search engines simultaneously and aggregate the results. Webcrawlers and spiders are automated programs that browse the web to index pages, while 'hits' refers to search results, not a search tool.