How to use a *.src web source file?
Copy or move the *.src file to the configuration folder at
%APPDATA%\Mp3tag\data\sources
You can also just execute the openSourcesDirectory.bat file that automatically opens the correct folder. It either comes with the *.src file or can be downloaded from here.
You can now use the script from the Tag Sources menu or from the 
button.
Please visit the Web Sources category if you are interested in more scripts.