Media Format Guidelines

Interactives

HTML Guidelines

• HTML may be written according to the HTML 4.01 Transitional, XHTML 1.0, or HTML5 doctype.
• All HTML files must declare a valid doctype. (HTML will be validated against W3C guidelines. It is suggested that all files are validated before submitting to PBS.  There are free utilities available to achieve this.)
• HTML must be Section 508 compliant.
• Interactive developers should follow best practices of web development for HTML, CSS, and JavaScript, including the use of non-blocking JavaScript loads and supporting the widest array of browser technologies possible.

Target browsers

The following is a list of target browsers:

• Google Chrome
• Firefox 60+
• Safari 14+
• Microsoft Edge

Interactive Package Construction 

• Interactives that contain multiple files should be delivered in ZIP archives containing all required files and directory structures needed to experience the object.
• At the root of the ZIP archive should be a manifest file called manifest.txt. The manifest should contain the following information, and nothing else:
• Title: Title of interactive
• Creator: Creator of interactive Creator
• Email: Email of interactive Creator
• Description: Short description of interactive
• Date Created: Date interactive was created
• The ZIP archive should also contain an index.html file at the root of the archive
• Only the index.html and the manifest.txt files should be located in the root of the archive. All other files should be contained in a subdirectory called content.
• Within the content directory, interactive creators may use whatever directory structure they choose, as long the guidelines outlined below are followed:
  • Reference files and directories with the correct letter case.  Filesystems are case sensitive. Capital letters may be used, but it is imperative for developers to realize that they must reference files and directories with the correct letter case. If the HTML, JavaScript, or CSS of your interactive references "filename.jpg" and the actual file is called "fileName.jpg" then your interactive may appear broken to the end user. This would cause your interactive to be rejected by PBS staff. (This is generally only a problem for developers working on case insensitive platforms such as Windows.) To avoid complications with filename references, it is recommended to avoid any uppercase letters in filenames.
  • Do not include spaces or special characters in file or directory names.  No spaces or special characters are allowed in file or directory names. The only special characters that are permitted are: dash ( - ), underscore (_), and period (.). So this-file_name.txt is valid, but this file~name.txt is not valid.
  • All linkage in any interactive should be self-contained and relative to the pathing within the zip archives. For example, the index.html file may embed the object content/css/main.css as a valid path and file. However, /content/css/main.css will not be a valid path or file on the production system.

• All interactives will be loaded via the index.html file in the root directory. This file should bootstrap the interactive to run for the user.

The structure of the content directory may take on a much wider variety of appearances. Figure 1 demonstrates a sample content directory.

Figure 1

Interactives are experienced through different platforms and devices. So in addition to designing the interactive for the appropriate audience, it is helpful to keep in mind some tips to make the interactive accessible for a variety of platforms and interfaces.

TIPS
Variable display resolutions	The interactives may be viewed on a wide variety of displays with varying resolutions so, where possible, use vector graphics. It is recommended that wherever possible, HTML-based interactives utilize a fluid layout in order to make the best use of available display resolution.
Avoid hover events	A hover event is any event that occurs upon hovering the mouse cursor over an object on the screen. JavaScript allows for this type of event.  These types of events should be avoided in order to better support touch-based interfaces. If an onHover event does not impact the actual functioning of a interactive, it is allowed. However, if an onHover event prevents users on a touch-based device from experiencing the core functions of a interactive, then those onHover events will require alteration.
Provide user -friendly interface	Although mouse pointers and other interface devices provide a high level of accuracy, it is recommended that interactive developers try not to position linked objects too closely together. Give some room to linked elements of your interactive, and allow hot zones to be as large as possible. This will make the interactive more accessible to differently abled users, will ease interaction with the interactive on touch-based devices, and will expand the audience to a wider age range (younger children tend not to be as precise with the mouse as adults and older children).
HTML links	When featuring HTML links as assets, provide the URL that takes the user closest to the media. PBS LearningMedia intentionally tries to avoid cataloging entire websites since we aim to feature discrete resources, so please avoid URLs to home pages, especially if the websites are large.