HTT means houkago tea time its the name of the band yui, ritsu, mio, azusa and mugi play in
moe means the qualities of a young girl, loli or bishoujo (young pretty girl, probably teen, in japanese) that make a man want to love her
http://www.urbandictionary.com/define.php?term=moe
http://en.wikipedia.org/wiki/Moe_(slang)