What are those blue highlighted input fields in the TAG editor?

Blue highlighted fields cannot be altered. This is the case because:

a) The MP3 file is READ ONLY, for example files on CD-ROM
b) The MP3 file contains TAGs of the newer version 2.x

Unfortunately the current verUnfortunately the current version of the program can only read those TAGs, saving is disabled. Thus the input fields cannot be altered. However, most MP3 files contain TAGs of ID3 version 1 or 1.1 Therefore this problem should not occur very often. BTW, the ID3TAG version can be found in the upper line of the TAG editor.