Web browsers
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Web Browsers - PowerPoint PPT Presentation

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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



  • 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

Web browsers

  • 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

Web browsers

  • 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

Web browsers

  • 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

Web browsers

  • 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

Web browsers

  • 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


  • 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


“What is the capital of Ohio”


“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 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

Web browsers

  • 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


WWW Server






Http cont

Status line


A blank line

Body if required


  • Request



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



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


( body of document)