You can ignore pollsters connected with special interest (trade associations, lobbies, unions, ethnic associations) and those that someone says uses questionable methods. Push polls in which the one statement is an ideological promise and the one involving the person asked about smear ("Do you approve of interracial sex?" followed by "Will you vote for John McCain who has a BLACK BABY?" -- never mind that the child is adopted from Calcutta) are to be avoided. Sometimes people catch onto a questionable methodology and if there is some apparent statistical fraud that suggests that the pollster is fabricating results you can and must ignore the poll.
You shouldn't ignore any poll. Instead, you should understand that those special interest polls can be biased, and should understand the reasons why.
But you probably should ignore Pbrower, and I need to learn to heed my own advice.