unable to find validator for simple type of attribute 'media'

```
This error message appears when validating an epub with different styelsheets
for different devices. I include the following lines in the head of each file:

name-of-file

The error message I get referring to these lines in each file is:
unable to find validator for simple type of attribute 'media'

Please could you let me know how to deal with this problem.

Thank you very much

What version of the product are you using? On what operating system?
Dreamweaver on Windows Vista

Read the ReportingIssues wiki page before submitting! In 99.99% of the
cases, you need to attach a minimal epub file to this issue so please do
so.
```

Original issue reported on code.google.com by `verydeep...@gmail.com` on 9 Dec 2012 at 1:09