The current guidelines recommend W3C technologies (e.g., HTML, CSS, etc.) for several reasons:
	W3C technologies include "built-in" accessibility features.
	W3C specifications undergo early review to ensure that accessibility issues are considered during the design phase.
	W3C specifications are developed in an open, industry consensus process
	Many non-W3C formats (e.g., PDF, Shockwave, etc.) require viewing with either plug-ins or stand-alone applications. Often, these formats cannot be viewed or navigated with standard user agents (including assistive technologies ). Avoiding non-W3C and non-standard features (proprietary elements, attributes, properties, and extensions) will tend to make pages more accessible to more people using a wider variety of hardware and software.
	Note. Converting documents (from PDF, PostScript, RTF, etc.) to W3C markup languages (HTML, XML) does not always create an accessible document.