An element embedded or referenced in the xHTML document of an ESEF report is not allowed to contain executable code (such as javascript, VB script, Shockwave, Flash) or references (such as hyperlinks) pointing outside the reporting package.
If the contents of the reporting package is in violation with the above, you will see one or two error messages: Violation: “executableCodePresent” or Violation: “referencesPointingOutsideOfTheReportingPackagePresent”.
This restriction is also why it isn't allowed to embed iXBRL viewers as part of the XBRL document. Simply because doing so would violate the restriction on embedding executable code.