Monday, November 29, 2010

HTML Uniform Resource Locators

A URL is another word for a web address.
A URL can be composed of words, such as "w3schools.com", or an Internet Protocol (IP) address: 192.68.20.50. Most people enter the name of the website when surfing, because names are easier to remember than numbers.

URL - Uniform Resource Locator

When you click on a link in an HTML page, an underlying <a> tag points to an address on the world wide web.
A Uniform Resource Locator (URL) is used to address a document (or other data) on the world wide web.
A web address, like this: http://www.w3schools.com/html/default.asp follows these syntax rules:
scheme://host.domain:port/path/filename
Explanation:
  • scheme - defines the type of Internet service. The most common type is http
  • host - defines the domain host (the default host for http is www)
  • domain - defines the Internet domain name, like w3schools.com
  • :port - defines the port number at the host (the default port number for http is 80
  • path - defines a path at the server (If omitted, the document must be stored at the root directory of the web site
  • filename - defines the name of a document/resource
Common websites start with http://. Pages starting with http:// are not encrypted, so all information exchanged between your computer and the Internet can be "seen" by hackers.
Secure websites start with https://. The "s" stands for "secure". Here, the information exchanged will be encrypted, making it useless to hackers.

Common URL Schemes

The table below lists some common schemes:
Scheme Short for.... Which pages will the scheme be used for...
http HyperText Transfer Protocol Common web pages starts with http://. Not encrypted. Unwise to enter personal information in http:// pages
https Secure HyperText Transfer Protocol Secure web pages. All information exchanged are encrypted, cannot be read by hackers
ftp File Transfer Protocol For downloading or uploading files to a website. Useful for domain maintenance
file   A file on your computer
gopher   A Gopher document or menu
news   A newsgroup
WAIS Wide Area Information Search A database or document on a WAIS database

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