Modem d-link DSL-300T

i have this modem and an hamlet adsl mode
i have a problem
using d-link mode when i try to enter in slow site , i can’t enter !!!
using the adsl modem it takes a lot of time ,but after some minutes i can see the pages

what can i do?
is there some setting that can help me?

this is a screenshot

problem solved!

dns of my provider are not right!

change dns and i 'm able to connect to the slow site