An automated tool can check if ALT text exists, but cannot tell if the ALT text is correct. For images that are not text, context must be considered. Consider, for example, this image of a lightbulb from New Zealands Ministry of the Environment. Thus, human judgment is required to evaluate ALT text for images, and the context of the images must be considered. The 508 NPRM requires that pages be readable without any accompanying style sheets.
Human judgment is needed to determine if the screenreader reading order makes sense.
The linearized reading order is backwards because the text is laid out in a table and some cells span two or more rows. The backwards reading order is a result of reading the table one row at a time. This example is made extreme to illustrate the importance of reading order, but there can be reading order problems in realistic web pages. The WAVE is a tool that helps a person determine if a web page is accessible. Except for special cases, the WAVE itself does not determine that there is an error.