The issue of Instructional Design technical standards, compliance, SCORM, metadata tests and W3C HTML validation came up in the course I am doing. This is an area best avoided, unless someone is paying you to do it, as it is frustrating, time consuming and never ending. The Australian VET E-standards is a reasonable overview.
One general point: Most learning objects are a ZIP file which contains folders, the folders have web format files for the content in them (HTML, CSS, JPEG, PNG). There are also some XML files with metadata (cataloging information) and quiz questions. E-books use a similar format.
The standards issue comes up with which version of file formats are used (HTML 4, XHTML, HTML 5 ...), what the folder structure is and what metadata is included. Vendors of products make claims as to what they support and educational institutions get stuck with particular products.
What I do is try to avoid using anything more than basic web formats for
my educational content, so that this will more easily convert from one
system to another. As an example, I use default formatting for headings
and text. I do not specify the font, color, or size of text, so it will
appear using the default of the system it is imported into. The result can look dull, but at least the student is likely to be able to read it and I don't have to spend hours fixing the formatting.
Just to show off, if you look through "IEEE Standard for Learning Object Metadata" (1484.12.1-2002) you will see my name it (I was on the balloting group, contributed one comment and then voted "yes"). ;-)