Can't copy (Ctrl+C) and make search (Ctrl+F) by formulae on feynmanlectures.caltech.edu. FF 18.0.2 works fine

When I select a text by the left mouse button , the formulae are not copied to the clipboard. Also browser skips symbols of the formulae from the search.

Tried in :

• Tor browser all versions (4, 5, 6)

• FF 18.0.2 https://sourceforge.net/projects/portableapps/files/Mozilla%20Firefox%2C%20Portable%20Ed./Mozilla%20Firefox%2C%20Portable%20Edition%2018.0.2/

Page for try: http://www.feynmanlectures.caltech.edu/I_13.html

Trac:
Username: Ilya_SpongeBob