Adding references for glossaries
1) If the definition is well-known and everyone uses it in the same way, you don't need a definition. If you use it in a certain way that might differ from others and thus needs to be defined, you should do so in the thesis itself, when the term first appears. Otherwise a reader might come to the wrong conclusions and only later realize that you meant something different by this term. Jumping back and forth to the definitions every time is also not that nice...
So I would suggest that you define the terms where you need them, where they appear in the work, and then add an index of symbols, only stating at which page each term gets defined (and maybe a one-line "name" of it) and no further definition in the index.

2) As you define the terms yourself, just like you need them, it won't be necessary anymore to use the homepage.
However, if you want to take definitions from there, you should say so. If you copy many definitions, you might want to say so at the beginning of the thesis or at the beginning of the chapter where the definitions appear.