Many non-W3C formats (., 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. When inaccessible technologies (proprietary or not) must be used, equivalent accessible pages must be provided. Even when W3C technologies are used, they must be used in accordance with accessibility guidelines. When using new technologies, ensure that they transform gracefully ( Refer also to guideline 6 .). Note. Converting documents (from PDF, PostScript, RTF , etc.) to W3C markup languages (HTML, XML ) does not always create an accessible document. Therefore, validate each page for accessibility and usability after the conversion process (refer to the section on validation ). If a page does not readily convert, either revise the page until its original representation converts appropriately or provide an HTML or plain text version.