The version of HTML, and the features within that version of HTML, should be selected based on the client environment of the target-user community. For example, “frames” and Java scripts are representative of the elements that reflect significant design incompatibilities with older browser versions, and are examples of the type of feature that must be given critical evaluation in the design phase. Removal of an architectural feature like “frames” can require significant redesign. Web page developers should be familiar with XML and evaluate how, if, and when to incorporate XML into a well-engineered Web site.

As a default, new well-engineered Web pages should use XHTML in its HTML compatible form. Some of the XHTML compatible guidelines should be included in the well-engineered Web site project plan, even where older browser compatibility is required (for example, lowercase tags.) Essential elements of XHTML compatibility: a) All tag elements and attributes in lower case.19 b) Documents to be well formed, have properly nested elements and have end tags on all elements that have content (including li, p, etc). Empty elements to have a closing slash in the tag (e.g.
—note space before slash in this example for HTML compatibility). c) All attribute values to be quoted. d) Use ‘id’ for fragment identifiers (in addition to ‘name’ for HTML compatibility, e.g. ). e) Use ‘[CDATA[…]]’ construct for enclosing script, style or other ‘commented’ elements (comment structures may be stripped by server during delivery process). f) Avoid linebreaks or excess spaces in attribute values. g) Do not include more than one ‘isindex’ element in a page. h) Include both ‘lang’ and ‘xml:lang’ values. i) Include both ‘xml’ and ‘http-equiv’ character encoding statements. j) Specify ampersand as & in attribute values. k) Be aware that CSS defines different conformance for XML and HTML

Cascading style sheets (CSS)

Well-engineered Web pages shall separate the presentation from the content, to the extent that it is feasible. Style sheets should be used to accomplish this. The trade-off between accommodating a greater range of target-client browsers using page-specific characteristics and the maintenance advantage of page-independent presentation offered by style sheets, shall be included in well-engineered Web site design. The decision to use CSS should include evaluation of the capability of target user environments.

A simple example is using color in Web pages. Explicit incorporation of color is one option; style sheet incorporation of color is another. The same color scheme can be applied to a diverse set of pages in a consistent way using a style sheet, reducing coding and maintenance effort. A change to the common style sheet, rather than changes to the many pages using that plan, can accomplish a change in the color scheme. Moreover, specific user communities may want or need to override the color selection put forward by the design (visual impairments for example), which is only viable with a mechanism such as cascading style sheets. Similarly, if hard-copy printing of a page is desirable, the CSS printer presentation style should be included. Web page generation tools shall support CSS as an external style sheet, only using site-developer specified/ selected ‘class’ (or ‘id’) attributes and avoiding the ‘important(!)’ designation so end-users can apply their own style sheets to match their preferences/requirements.

A simple example is using color in Web pages. Explicit incorporation of color is one option; style sheet incorporation of color is another. The same color scheme can be applied to a diverse set of pages in a consistent way using a style sheet, reducing coding and maintenance effort. A change to the common style sheet, rather than changes to the many pages using that plan, can accomplish a change in the color scheme. Moreover, specific user communities may want or need to override the color selection put forward by the design (visual impairments for example), which is only viable with a mechanism such as cascading style sheets. Similarly, if hard-copy printing of a page is desirable, the CSS printer presentation style should be included. Web page generation tools shall support CSS as an external style sheet, only using site-developer specified/ selected ‘class’ (or ‘id’) attributes and avoiding the ‘important(!)’ designation so end-users can apply their own style sheets to match their preferences/requirements.

XML considerations

XML provides mechanisms for delineating document structure in ways that are responsive to business objectives. A well-formed HTML document is one instance of an XML document. XML provides for new tags that can be content specific, and facilitate automated processing of content. Within the HTML environment, XML-type structures should be designated with the id and class attributes, and potentially the and elements. Within an HTML 4.0 document, id is defined as being unique, and can be used as an anchor for fragment links, whereas class can be duplicated many times within a document. Both id and class can be used to distinguish a page segment for style sheet presentation control (developers should verify that usage of ‘class’ and ‘id’ for style specification work for the targeted range of browsers). Well-engineered Web sites may plan for the accommodation of a range of browsers identified in the targetuser community client environment during the design planning process. This can be accomplished by identification of browser types and delivery of different sets of pages based on this, or by ensuring that the critical information content for a page can be effectively presented by the full range of browsers. Browser and version-specific dependencies should be avoided.

Physical characteristics

Consideration shall be given to the legacy and anticipated evolution of the user-community environment in terms of hardware and software capabilities. The rate of adoption of new technology at the consumer level often exceeds that of industry and the public sector. Similarly, consideration shall be given to anticipated or likely changes in technology to minimize the need to re-engineer Web sites to accommodate these changes. Some examples of devices that should be considered include:

a) Personal Digital Assistants (PDAs) b) Video enhanced telephones c) TV devices with Web interfaces d) Braille display units e) Access-specific and/or text-only devices f) Wireless and mobile devices Considerations should include screen display area (which can be quite small on some of these devices); latency of communications (e.g., satellite links, wireless channel bandwidth, etc); and, limited (or non-existent) local cache/storage. Similar considerations related to communications bandwidth and costs are required. U. S. communications tariffs are not exemplary of international practices. Limited bandwidth and “per minute” tariffs are common on an international basis and in the emerging mobile and radio communications environments.

Protocols or protocol subsets to support this next generation of mobile devices may require additional consideration in selection of target protocols. Consideration should be given to the wireless applications protocol (WAP), and XHTML base protocol. Note that rapid expansion of low bandwidth wireless devices in the next few years may be a significant consideration in Web page design.