Research the owners of a fake ID site
I do recommend you buy only from legal novelty ID sites listed here, but if you want to take a chance with your hard-earned cash and buy an illegal fake ID from some website, there are a few things you can do to research who is behind the website before you order.
All websites have a domain name - the domain name of this site is "fakeid.uk.com". The details of the person who registered the domain are available by using a service called whois. To reseach a domain, simply go to who.is and type the domain name in and click "search". You will then get the results back.
I've done an example search on "bbc.com" - see below.

Things to look for:
You want to see that the website is registered to a real company or business. If the site is based in the UK, it should be registered in the UK
The older a website, the longer it has been in business. This is usually a good sign of reliability. Many scammers register a domain name for one year, then move on to a new domain name. This is a classic scam as if you google the scam website, there will be no complaints to be found if it is a new domain name.
You certainly would want to think long and hard about sending your money to a site that is based in a foreign country. Business registered in China are pretty much untraceable if they scam you out of your money.
Things to note :
Whois details can be completely false and made up.
The contact details can be totally fake.
The email address for the registrant may not work.
Some registrants use a privacy service, if this is the case you cannot tell who owns the site. While this is not an indication that the site is a scam, it may make it harder to get in touch with the site if they scam you or do not answer email.