I am currently studying the Hubble Constant as part of my high school physics course. I'm aware that inaccuracies in determining this constant are largely due to difficulties in measuring distance between galaxies. I really just wanted some information, or to be directed to some web sites that I can follow at my level as to how in fact distance is measured in this context. I have read a little bit about Cepheid Variables but I don't really follow the concept. Perhaps someone with more knowledge could enlighten me on how the data to determine this constant is obtained.