For a brief explanation how to use this program, go here.
Credits: the web interface was designed by Shaohua Xie and the programs were written by Jan Mrázek, Xiangxue Guo, Shaohua Xie, and Anuj Srivastava with the use of ClustalW and John Brzustowski's qclust.
Reference: Mrázek, J., Xie, S., Guo, X. and Srivastava, A. (2008) Bioinformatics 24, 1041-1048.
Note: this is a free service provided without any warranty explicit or implied.