I saw that the link opens many pop-ups that difficult the reading.
I have found two more(in Spanish, too) without pop-ups. The first is very clear and easy to read; the second is a bit difficult because of letter size, but it has complementary information:
http://usuarios.lycos.es/lossantos2/heraldica/alvarez.htm
http://www.surnames.org/apellidos/alvarez.htm
Lumia
http://onomastica.mailcatala.com