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Although a standard web page allows the author to do many things, some effects can only be achieved by using particular add-on applications.
A web author must bear in mind that each of these files will add to the document weight and download times for the user, and will complicate the accessibility of the page for many.
As well as the author requiring proprietary software to construct these added extras, the end user will also require proprietary software to make use of them.
Such software is usually available to a user free of charge but can take some time to download and install.
Use each checklist to ensure that your web pages comply with these guidelines
4.5.1 Checklist and summary: Core guidance
Checklist
Summary
Many plug-in technologies are available to a web author, each offering possibilities for presentation and content that cannot be achieved in standard HTML pages.
Plug-ins require the content author to have the skills and relevant software to construct the files, and the end-user to have the (usually) free reader software for the plug-in application on their browser.
Training, development and implementation costs will have to be considered by an organisation, as well as the end usability of the website.
Wherever plug-ins are used accessible alternatives must also be provided.
4.5.2 What plug-ins are
Web browsers interpret and display the HTML and CSS content contained in web pages. Most web browsers are also capable of rendering text and image content generated from the JavaScript scripting language and the Java programming language.
In addition, most recent web browsers have the ability to extend the repertoire of file formats they can process by means of software plug-in components.
The following are short descriptions of some of the most popular plug-ins used on websites today.
4.5.2.1 Portable Document Format (PDF) [Adobe Corporation]
This is probably the most common plug-in and helper software on the web today. A document saved as a PDF file retains its entire document layout, including images and font formatting. Any user can now download this file using the free Adobe Acrobat Reader software. Once downloaded, PDF files can be read on screen, saved to local disk or printed.
Adobe Acrobat Reader (free) [External link]
4.5.2.2 Flash [Macromedia]
This plug-in is popular for websites that are required to convey interactive graphical information, such as animated menu disclosures. The image files are stored in vector format, which allows users to zoom in on images without them degrading. The files’ size could be a major limitation to the popularity of the format, but this is overcome by streaming. Streaming allows the start of a file to play while the rest of it is downloading, thereby giving users rapid access to the content no matter what the speed of their modem.
Flash player (free) [External link]
4.5.2.3 Shockwave [Macromedia]
Websites that include this plug-in are referred to as ‘Shocked’ sites. A popular plug-in, it is used for more sophisticated interactive animations, such as, demonstrations, presentations and games that require the full power of a sprite-based animated system. Shockwave filesizes can be large.
Shockwave player (free) [External link]
4.5.2.4 Quicktime [Apple Corporation]
This plug-in is a very versatile application for the playing of digital video and audio on the web. Although this plug-in was developed by Apple Computer, it can be used by any operating system. It will play many-streamed video and audio formats.
Quicktime player (free) [External link]
4.5.2.5 RealPlayer [RealNetworks Inc]
One of the main uses of this plug-in is to allow real-time television and radio transfers across the web. The viewer is very user friendly although there are significant privacy concerns over the information that is elicited from users as part of the installation and registration process.
RealPlayer Basic player (free) [External link]
4.5.3 Usability considerations
All the above examples require proprietary software to construct and to view the files. Each can be useful and informative to a user if used in an appropriate manner.
It must be remembered that each different example that is used will require the user to have the plug-in already installed. If a user does not have a required browser plug-in installed, they will have to download it, which can be a lengthy and confusing process to users not used to downloading and installing software. These sites often based in the USA and download times can be anything from 2 to 20 minutes.
If information that is formatted and contained within a plug-in is essential to the user, the data must also be formatted in other ways.
A ‘Flash’ presentation is quite acceptable in a website as long as it is not on the organisation’s homepage and an HTML version is delivered first from the same location.
Plug-ins should never be needed for files on a department’s homepage or other major locations.
Any file requiring a plug-in must also carry an explanation of the data in the file. There must also be a clearly defined link to a replica of the data in static HTML.
All video and audio formats will cause difficulty for certain sectors of the web-using community. Whenever these are used, text versions should be available, either within the plug-in (using closed captions or speech) or as a separate HTML file containing the transcript.
The corporate user:
Web managers must be aware that many corporate users are prohibited by security measures from downloading plug-ins or adding additional software to their workstations.