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Web Browsers. CS 3505. Wb_webBrowsers-I.ppt. Vendors. Major web browsers: Netscape and Microsoft IE, Firefox , Opera 8 AOL uses a browser that’s re-branded IE (I think). They’re free A few others out there: lynx (text-based), etc. URLs. The URL: http://www.microsoft.com/office

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Web browsers

Web Browsers

CS 3505

Wb_webBrowsers-I.ppt


Vendors
Vendors

  • Major web browsers: Netscape and Microsoft IE, Firefox , Opera 8

  • AOL uses a browser that’s re-branded IE (I think).

  • They’re free

  • A few others out there: lynx (text-based), etc


URLs

  • The URL: http://www.microsoft.com/office

    • http is the protocol

    • www.microsoft.com is the server name

    • /office is the file on that server


URLs

  • ftp://ftp. nps.navy.mil/

    • ftp is the protocol

    • ftp.nps.navy.mil is the server

    • Logs you onto the ftp server as user “anonymous” with ?? As password.

NPS FTP does not work well try ftp://ftp.microsoft.com


URLs

  • news://news.mbay.net

    • news/nntp is the protocol

    • news.mbay.net is the news server

    • Launches news reader

  • gopher:// hardly ever used these days

  • https:// is secure http (more later)


What the url means
What the URL means

  • Http: “Using the http protocol”

  • machine name: “Connect to this machine”

  • file name: “starting from the default point for documents on this web server, retrieve this document”


Url example
URL Example

  • Example: http://www.nps.navy.mil/cs/Faculty.asp

  • On the site www.nps.navy.mil, the Web server will look for the file

    • CS/Faculty.asp


Default index file
Default index file

  • Usually you can just specify the directory you want to look in. By default the server will look for a file usually called “index.html” within that directory.

  • Index.html or default html is usually the top file of a web site

  • Also htm and html are alternative dialects


Other types of files
Other types of files

  • You can configure your web browser to cooperate with types of files other than html

  • You can configure it to launch a “helper application” or “plugin” when it encounters a file. A plugin is a program that runs inside of your browser. A helper application launches external to the web browser.


Plug ins and helper applications
Plug-ins and Helper Applications

  • View plug-ins:

    Tools->Internet Options->

    _General->Settings->View objects_

  • Programs tab

  • File extension mechanism


PDF

  • Adobe Portable Document Format

  • Postscript-like control of graphics in the document

  • Free viewer from adobe

  • Can either be viewed as a plugin or an external viewer


VRML

  • 3D environments

  • Usually done as a plugin

  • .wrl extension


Browser features
Browser Features

  • Top tool bar

    • Back , forward

    • Refresh , update local copies

    • Home ; set home page Tools->Internet Options


Bookmarks
Bookmarks

  • An easy way to save a place on the web

  • Called “Favorites” in Internet Explorer

  • “History” provides a list of sites visited

    • Today,Last week, 2 weeks,3weeks


Cache and refresh
Cache and Refresh

  • Browsers copy html files to local disk and retrieve from the stored copy

  • Change Cache settings

    Tools->Internet Options-> temporary internet files-> settings

  • Location example:

    C:\Documents and Settings\userID\Local Settings\Temporary Internet Files


Searching the web
Searching the web

  • Click “Search” on IE

    • Enter key words on pop up

    • Uses MS Search engine

  • Go to A search engine

    • Yahoo.com, AltaVista.com, Google.com

    • Enter key words


Key word searches
Key word searches

  • Return all key words

  • Example:Terrain Images

  • Will return references to all indexed pages which contain the word

    • Terrain

    • Images

  • Lots of “hits”

  • Presented in an order as determined by the search engines “evaluator rules”

  • Often paid advertisements are the primary order

    • Yahoo was “pure” until recently


Advanced boolean searches
Advanced Boolean searches

  • Most search engines have Boolean rules usually available through a help or advanced search button

  • Typical Advances search options

    • Match all words(AND)

    • Match any words(OR)

    • Group whole phrase(“ “)

    • Do not include (NOT)

  • Example Yahoo the OR is implicitly coded as a blank

  • Natural gas prices in Washington State

  • Will get hits on all words except articles(in, a, of..)

  • Reduce the search by applying rules

  • “Natural gas prices” “Natural gas cost” Washington NOT DC


Search trick
Search Trick

* Often the whole or part of a web page has been indexed thus one is searching for a phrase in a page.

* Think how the question would be answered not how it would be asked

* NOT

“What is the capital of Ohio”

*Instead

“The capital of Ohio is”


Saving and viewing information
Saving and Viewing Information

  • View->refresh

  • File ->Print

  • File->save As

  • Save Image

    • Right click on image, save as

  • View->source


Secure transmission
Secure Transmission

  • Recall that messages and files sent across the internet are plain text and can be intercepted

  • SSL uses encryption to send files and messages across the net. This is done with secure http, https.

  • A bit slower than http, but fast enough

  • https and a little icon of a lock show you’re secure


Example amazon com
Example: Amazon.com

  • Https:// and lock icon when using secure server, http:// and no lock icon or unlocked lock icon for unsecure server

  • Warning


Cookies
Cookies

  • Cookies are used to implement things like shopping carts

  • Web servers can’t remember information from one transaction to the next easily.

  • Cookies are just a place for a web server to store data

  • Location example:

    C:\Documents and Settings\userID\cookies

  • Control Coockies:

    tools->internet options->

    Security-> custom level


HTTP

  • Http is the protocol used by browsers and servers on the web

  • Very simple request response sequence

  • RFC 2616: Hypertext Transfer Protocol -- HTTP/1.1

http

WWW Server

(apache)

Browser

(netscape)

request

response


Http cont

Status line

Headers

A blank line

Body if required

HTTP(cont)

  • Request

Method

URL

HTTP Version

Main Methods: GET, HEAD, POST

Others; Put, Patch, copy, move, delete, link, unlink, option

  • Response

  • Mime like

  • Status codes

    Example: 302-moved


Http example
HTTP example

client

server

GET /usr/bin/image1 HTTP1.1

Accept: image/gif

HTTP/1.1 200 OK

Date: mon, 07-jan-02 13:15:14: GMT

Server: Challanger

MIME-Version: 1.0

Content-Length:2048

( body of document)


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