There's a danger, when researching one's family history to get over-excited and start to rely on information which may be less than 'safe'.
For example, the IGI put together by the Mormons is of fantastic value to genealogists but a lot of information and pedigrees contained within their archives are guesswork, strung together by people who are using nothing more than wishful thinking and then submitted to the LDS as fact.
These dodgy pedigrees can then be picked up by someone who is researching a particular name and the information added to their line of ancestry based on nothing more substantial than the fact that they sourced it at the IGI so it 'must be right'.
In england, parish records started in 1538. Not many parishes still have records which go back this far. Before 1538 there are no set, country-wide records which can help trace a family line. If you haven't traced a line to royalty by 1538 you're more or less scuppered.
Even if you do find a direct line back to some monarch or other, royal pedigrees may well be 'fiddled' and should be regarded with suspicion. The real heir to the throne of England is apparently an Aussie fork lift truck driver called Mike

I'm one step (and boy what a mountain of a step it's proving to be!!) away from tracing a direct line back to a Philip Ible, born 1566 in Herefordshire (not royalty I'm afraid, just a humble peasant like me). At the moment I can only prove my line back to 1792. I need to find official records to make the link to Philip. I can't rely on a pedigree placed on the IGI, much as I'd like to.

Anyone considering starting their family history - take each generation a step at a time and make sure the link to the previous generation is safe (usually with official documentation) before moving on. As the 'kids' of today would say - 'Keep it real'

Cheers,
Bryan.