Yes, I can say that 90+% of all internet poll's are useless. But of course it is what statistics your after to start with.
If GTPlanet (admin's) hold a poll, they have detailed information about population of their website etc etc.
So then they know how big the group is that actually didn't participated in the survey.
But a poll on your favorite news website, is very selective and can often not be counted as what the country/world would do. because the "population" on that news website is selective to start with.
Always a certain group of people that reads a specific website.
Research never been an easy job.....