The "www" tag causes massive problems at the newest mp3tag version (2.46b)!
In ID3v2.3-Tags www-tags are not read by mp3tag. Even with files which I have tagged with an earlier version of mp3tag (most of my files). The tags are still present, because I can read them with my mediaplayer (foobar2000).
When I edit these files with mp3tags the www tags get lost (they don't appear in foobar anymore).
When I write a new www tag with mp3tag, it simply disapears at saving.
I noticed by chance that ID3v2.2 & ID3v2.4 www tags are still read correctly by mp3tag. But when I edit them with mp3tag they are transformed to ID3v2.3 tags and the www tags get lost.
I also found a file with a ID2v2.3 (ID3v1 Lyrics3v2 ID3v2.3) with a www-tag displayed at mp3tag. At saving, the www-tag disapeared in mp3tag, but it is still there in foobar. The tag type ID2v2.2 (ID3v1 Lyrics3v2 ID3v2.3) is not altered to something else.
When i edit the www-tag in foobar, it re-apeares in mp3tag. But only if I edit the www-tag, not if I edit another tag in the same file. In both files, the tags are transformed into ID2v2.4 (ID3v1 Lyrics3v2 ID3v2.4) tags by foobar.
After more searching i found now some files with ID3v2.3 (ID3v1 ID3v2.3) tags with correctly displayed www-tags. At saving they disapear, but are still there in foobar.
So, putting all together I must say that I have no idea when the problem occures. But I'm sure it wasn't there in mp3tag 2.46a.
It's rather annoying, because I constantly loose information when i re-tag old files and I don't get full information when i run my web sources scripts which all write the www-tag. So I will use the v2.46a until this is solved.