*IN PROGRESS* WEB TECHNOLOGIES Flashcards
(19 cards)
Describe the purpose of HTML and CSS within the code of a website
- HTML defines the structure of a web page
- HTML defines the content of a web page
- Using tags (englosed in <>)
- CSS defines the style/appearance
- Using selectors such as classes/IDs/etc
- Can be placed within HTML or externally in a file
- Multiple pieces of CSS can be combined (the more local instances overriding)
Explain why server side processing is used to recalculate a booking fee
- Processing done away from the user’s control (client side processing could be altered)
- Browser may not support client-side language
- Booking fee calculation needs to be correct for all locations
State what is meant by the term ‘damping factor’
- A value between 0 and 1
- Probability that a user will not follow a link
- Prevents PR(Tn)/C(Tn) form having too much influence
- Notionally set to 0.85
Give the factors that affect the output value given by the PageRank algorithm for a website
- Number of links to target site
- PageRank score of those sites (linking inwards)
A web development company is looking to recruit a programmer to build websites.
Discuss the technologies the programmer would need to know and use and the importance of each one.
- HTML
- They know how to write (i.e. define the structure of) web pages
- CSS
- They understand how to define the formatting of websites
- JavaScript
- They understand how to write client side code
- Allowing them to add interactivity to the website
- Understanding HTML/CSS and JavaScript is essential for the role. WIthout knowing HTML it is impossible to handcode web pages.
- Whilst WYSIWYG tools exist these often produce inefficient code and at any rate it will be necessary at some point to hand tweak the code
- CSS is nearly as essential. Whilst HTML can be used for a lot of formatting, this is considered bad practice.
- CSS will allow them to make consistent looking sites
- JavaScript is also essential as most websites have an interactive element (e.g. validation of forms)
- Knowledge of server-side processing
- Allowing them to write dynamic websites
- This is important if the company wants to produce websites with content that changes
- Databases
- Allowing them to allow websites to store and retrieve data
- Some knowledge of databases will be useful if writing dynamic sites. This will largely be focussed around SQL
- Photo editing
- Allowing them to prepare images for the website
- This is less essential as in many cases the assets will be pre-prepared. A basic knowledge (e.g. resizing would be expected)
- Knowledge of software engineering practices
- Allowing them to work as part of a team when building a website
- The importance of this will depend on the size of the team working on the site
Describe why a website might use CSS
- To define the formatting of a website
- To change the formatting depending on device
- To give a consistent look to every page
Explain the difference between a HTML id attribute and a HTML class attribute
- Only one element can have a given id
- Class can be assigned to multiple elements
Discuss the difference between server and client side processing with respect to web pages. You should refer to the advantages, drawbacks and best uses of both approaches.
- Server side processing takes place on the web server
- Data is sent from the browser to the server, the server processes it and sends the output back to the browser
- Client side processing takes place in the web browser
- Client side processing doesn’t require data to be sent back and forth meaning code is much more responsive
- No need to submit to server and wait for response
- Website will work more quickly for user
- Reduces load on the server
- WIll need to spend less on processing power/bandwidth
- Code is visible which means it can be copied
- The browser may not run the code either because it doesn’t have the capability or because the user has intentionally disabled client side code
- Server side processing takes away the reliance of the browser having the correct interpreter
- It hides the code from the user, protecting copyright and avoiding it being amended / circumvented
- Server side processing puts extra load on the server. This is at the cost of the company hosting the website
- Client side processing is best used when it’s not critical code that runs. If it is critical then it should be carried out on the server.
- Client side processing is also best where a quick response is needed - an example being games
- Server side processing is best used where it is integral that processing is carried out. It is often used for generating content.
- It can be used to access data including secure data.
- For this reason any data passed to it has to be checked carefully.
- With some things like validation good practice is to do both: First on the client for a quick response if there is an issue, then on the server in case the client side processing has been circumvented
The owner of a website notices that his site doesn’t come up high in the results from a search engine that uses the PageRank algorithm. State what would affect his site’s ranking
- The number of sites that link to their site
- The PageRank of the linking sites
- The number of outward links from the site
Many websites try to ensure they are accessible to all visitors regardless of disability, language
spoken or the device being used to access it. Discuss the technical and design measures that can
be taken to ensure a website is accessible.
Using text alternatives for images
Changing styles using CSS
Avoiding combining colours that may be indistinguishable by those with
colour blindness.
Using character sets and fonts that support different alphabets.
Using server side processing to amend the content shown.
Writing web pages to facilitate screen readers (such as giving hyperlinks
meaningful names and not just “click here”).
Using tables for tabular data (as they are intended) and not layout (again to
aid screen readers).
Ensuring that all content can be accessed with the keyboard alone in a
logical way.
Avoiding CAPTCHA.
-Using the alt attribute with the img tag allows descriptive text to be shown
where the image cannot be loaded or the user has disabled images (e.g. a
screen reader).
-By having multiple external style sheets the look of the page can be
switched. This might include changing the layout for smaller devices or
increasing font size and contrast of colours for people who are visually
impaired.
-JavaScript may be used to allow users to switch style sheets without having to reload the page
-Choosing colours is important as to people with colour blindness might for
example not be able to see green text on a red background.
-Designers also need to have an awareness of the cultural meanings of
colours.
-Use of Unicode supports all character sets.
-If the website is processed Server side the content itself can be changed
according to the user. The language used may be determined by the user’s
IP address. Cookies may be used to save the user’s preferences.
Simple design considerations can have a positive effect on accessibility.
Colours and fonts affect readability. A good design can be accessible to a
wide audience. Standards exist to help maximum accessibility for those with
disabilities.
Use of web technologies can then personalise the output to help ensure the
site is specifically accessible to the individual.
Describe how a website is indexed by a search engine.
Web crawler /spider visits site
Either be selecting it from an existing list or
following a link.
Records information
…such as text/meta tags/etc
Records the position of each word within the page
Storing them in an index
Follows links to other sites
Robots.txt file can be used to instruct web crawlers
Explain what client side processing may be used for and why they are used
- Initial data validation (JavaScript)
- Manipulates user interface elements
- Applies website styles (CSS)
- Reduces load on server
- Reduces the amount of web traffic
Explain what server side processing is used for
- Providing further validation of data
- Queries and updates the server database
- Encodes data into readable HTML
- Keeps organisation data secure
- Performs complex calculations
What is the PageRank algorithm
- An algorithm used to help compile and rank website pages and the list of results returned by a search engine
- It works by checking the number and quality of links to a page in order to determine roughly how important that page is
- The assumption is that websites of greater importance are more likely to be linked to from other websites
PR(A)
The PageRank of page A
C(Tn)
- The total count of outbound links from web page n, including the inbound link to page A
PR(Tn)/C(Tn)
The share of the vote page A gets from pages T1 through Tn
What should you know about how the PageRank algorithm is applied for the exam
- A web page’s PageRank is determined in part by the PageRank of other pages linking to it
- The algorithm works without needing to know the PageRank of any back-linked pages
- In the first instance, the algorithm makes an informed guess. After several further iterations, the algorithm begins to home in on the correct PageRank
- The number of iterations required for the final PageRank number to stop moving can be hundreds - if not millions
- Once the final PageRank is achieved, the average PageRank of all pages will be 1
PR(Tn)
- The PageRank of page n
-Each web page has a notational vote of 1, shared between all the web pages it links to
