Web Browsers CS 3505 Wb_webBrowsers-I.ppt. Vendors 4 Major web browsers: Netscape and Microsoft IE,...
-
Upload
daniella-bradley -
Category
Documents
-
view
218 -
download
0
Transcript of Web Browsers CS 3505 Wb_webBrowsers-I.ppt. Vendors 4 Major web browsers: Netscape and Microsoft IE,...
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
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
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
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
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 View plug-ins:
Tools->Internet Options->
_General->Settings->View objects_
Programs tab File extension mechanism
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
Browser Features Top tool bar
– Back , forward– Refresh , update local copies– Home ; set home page Tools->Internet Options
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 Browsers copy html files to
local disk and retrieve from the stored copy
Change Cache settingsTools->Internet Options-> temporary
internet files-> settings
Location example:C:\Documents and Settings\userID\Local
Settings\Temporary Internet Files
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 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 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
* 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
View->refresh File ->Print File->save As Save Image
– Right click on image, save as
View->source
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
Https:// and lock icon when using secure server, http:// and no lock icon or unlocked lock icon for unsecure server
Warning
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
Browser
(netscape)
WWW Server
(apache)
httprequest
response
HTTP(cont)
Request
Method URL HTTP Version
Response Mime like Status codesExample: 302-moved
Main Methods: GET, HEAD, POST
Others; Put, Patch, copy, move, delete, link, unlink, option
Status line
Headers
A blank line
Body if required