If you have a population of 1,000,000 people, how many to be sampled to give a representative profile with only a 5% point margin of error ?
You have not provided enough information to answer that question. First, you need to specify an alpha for a desired confidence level (e.g., with 95% confidence, the margin of error is within 5%) Second, you have not specified what it is you are measuring. Is it a binominal (yes/no) question, or is it a population mean, or is it a population distribution, or is it something else).
In the mean time, check out the wikipedia site for a discussion of determining the sample size to generate a desired margin of error.
http://en.wikipedia.org/wiki/Margin_of_error