use the filter command. you need to list each site you want to block like this -
pix1(config)# sh filter
filter java 80 0.0.0.0 0.0.0.0 10.1.1.1 255.255.255.255
filter java 80 0.0.0.0 0.0.0.0 20.2.2.2 255.255.255.255
filter activex 80 0.0.0.0 0.0.0.0 11.11.11.0 255.255.255.0
filter activex 80 0.0.0.0 0.0.0.0 99.99.11.0 255.255.255.0