As stated by the Food Standards Agency
Does a food business have to show its rating?
No, so if you see a business without a hygiene rating sticker or certificate, you'll have to decide if you want to eat or buy food from there without knowing the hygiene standards.
Putting a hygiene rating on show is a good advertisement for businesses that meet the requirements of food hygiene law.
A good food hygiene rating is good for business
More can be found here
http://www.food.gov.uk/multimedia/webpage/faqsen#elem007a
As a Catering Manager I am proud to show off my 5 stars which my team work hard to achieve and maintain. (No not an establishment in Dover)
When the inspector calls they will score against the following:
•standard of the structure, equipment and cleaning
•food handling practices
•confidence in food safety management
The rating is as follows:
•5 Star - Very Good
•4 Star - Good
•3 Star - Generally Satisfactory
•2 Star - Improvement Necessary
•1 Star - Major Improvement Necessary
•0 Star - Urgent Improvement Needed
It is hoped that this information will:
•allow you to make an informed choice about where you eat
•encourage food businesses which have high standards to continue to maintain them
•encourage those food businesses that have poor standards to improve
Since the scheme was introduced I do now look more closely for restaurant scores, not only in windows but also on line. It can make interesting reading. Its worth looking up a restaurant you are intending to visit