Online polls are popularity contests that the most excited people answer.
They don’t sample.
There are scientific online polls and there are non-scienticic online polls.
It is possible to get lots of samples and create a sample of groups balanced according to known demographics.
Over time the averages of the groups are more and more likely to reflect the total world of Internet users.
Which today is about everyone from 70 on down.
“Online polls are popularity contests that the most excited people answer.”
No, there are website polls which are as you describe, and then there are scientific polls which are administered online rather than by phone interviews. Zogby, Reuters/Ipsos, and LA Times/USC are all examples of this.