How do we know if an MP3 file converted by LAME Codec or Fraunhoffer Codec?
You can download the freeware version of Encspot here .
It gives quality info as well as details of the encoder.
the quality ‘flag’ isnt very accurate, however ;). it merely judges by bitrate.
WOW 
thanx a lot YogiBoar
Helium2 has a great tool for testing the quality of mp3’s and a program called mp3utility can also test your mp3’s for sync errors.
Both give good indications if the songs are any good.