"Firefox 30 hangs" fix found Rated 5 out of 5 stars
Problem in the Firefox profile, subdir \tidy which contains the file 'spvalid.err'. Normally this file is zero bytes, with no data. The file had been 'restored' from another PC running a different o/s. Removed subdir \tidy, then re-installated Add-in which has repaired the issues and HTML Validator is now running as anticipated. Thanks to Marc for hint about Firefox profile.This user has a previous review of this add-on.