Web technologies Flashcards
Exchanging data
What is HTML and what is it used for
HyperText Markup Language
- Used to define web pages
How does HTML work
It works with tags that are used to denote what parts of the page represents
most tags have an opening tag (e.g.<html>) and a closing tag (e.g. </html>)
What attributes do images use (HTML)
- ( arc ) to define where the image is stored
- ( alt ) to define what text should be displayed if the image cannot be shown
- ( height and width ) to state the dimensions of the image on the screen in pixels
What are cascading style sheets (CSS)
Take on the job of styling pages
- To specify a styling in CSS you need a property and a value (e.g. colour: red; )
define backround-color (CSS properties)
specifies the background colour of an element
- Usually used on <body> tags to change the background colour of the whole page
- Used with <div> tags to just change part of it
background-color: LightGreen;
define border-color
Specifies the colour of the border
- Tends to be used on div elements
border-color: DarkBlue;
Define border- style (CSS properties)
Specifies the style of the border
- Options include dotted, dashed and solid
(if not specified, the border style is none by default and no border is shown)
border-style: Dotted;
Define border width (CSS properties)
specifies the width of the border in pixels
border-width: 3px;
define color (CSS properties)
Specifies the colour of text within an element
color: #2566A1;
color: green;
define font-family (CSS properties)
Specifies the font of the text
font-family: monospace;
What are the two ways colours can be specified in CSS
- 140 standard colour names can be used as they have been assigned a name in CSS
- Hexadecimal colours
Why do we need JavaScript
If we want to program things to happen within a page (e.g. checking whether data being entered is valid)
What is a search engine
A website used to find other websites. Users type in search terms and are given lists of web pages that match them
What is a spider/web crawler
A program that visits websites adding terms from them to a search engine’s index
How do search engines work
- They create an index of words that appear on pages ( it will store the address of the page the word appears on and its location on the page)
- They use web crawlers that visit a web page and index the words that are on the page
They can follow the links on the page to go to the next page to be indexed - When a search term is entered the search engine will look for pages that contain all the words entered
what is the PageRank algorithm
An algorithm that determines the importance of web pages, considering the number of incoming links a page has and the PageRank from which those pages come.
The algorithm is recursive; it uses the existing Pagerank of pages as part of the calculations for their new PageRank.
What is the process when accessing a page
1) the browser requests a page from the server
2) The server runs its scripts to produce a web page back
3) The browser receives the page from the server, readers the HTML and CSS and runs any client-side scripts needed
Advantages of client-side processing
- Web traffic is reduced
- There are fewer delays as the server does less processing
- Data can be validated before being sent to the server
What is server-side processing
- Scripts can access databases located on the server
- It must be guaranteed that a script will be run in the way intended and cannot be amended or circumvented by the client
