I have to disagree. As one who works with several high volume web sites these errors being sent are taking up bandwidth particularly on FT's end. Not to mention that firefox's performance (ergo FT's performance) will be affected while firefox detects and logs these warnings/errors.

To just say that lots of sites have these warnings/errors doesn't make the FT site technically correct or efficient. Because there are also a lot of sites that don't have any of these warnings/errors.