Type 'easy' or 'hard' to begin the quiz. Easy is a 5-degree grid, hard is a 2.5-degree grid. Then, try to name the LARGEST European city in each grid square which fits the category label for each square. To name a city, you must first click on the grid square to make it have a GREEN border. Then, type in the city answer for that square followed by a '.' (a period). You are given a score from 0 to 100 based on your answer's population compared to the largest city accepted in that square (100 being you named the largest city).
LETTER: means the city starts with that letter.
NUMBER RANGE: (such as 2-5, 10+) means the city contains that many letters (excluding spaces and special characters).
POPULATION RANGE: (such as 50-100K) means the city has that range for its population.
2+ WORDS means the city name has 2 or more words (words denoted by a space or hyphen).
At the end of the quiz the largest population missed answer will show in each unanswered square, and for those answered the largest city will be listed if you didn't answer it.
Quiz Takers 
the locations of the cities are very of, never in the center of the cities just vaguely in the right area.
Yeah the city centroids are based on the border of the whole city I believe.
These seem to be based on urban areas and some of the pins (Thisted for example) are way out in the countryside.
I think it’s just poor cordinates, A lot of the cities have pins right on a square border. Thisted is perfectly at 57N, Herning is perfectly at 9E. Hjørring and Brønderslev are perfectly at 10E, Helsingør is perfectly at 12º30’E, Vejle is perfectly at 9º30’E. etc.etc.
It’s centers of the boundaries I think based on the source (citypopulation), so yeah some aren’t going to appear right in the actual center of the populated area.
The pins on citypop are all accurate. I think you might be getting the municipal seat cordinates from the municipalities instead of the actual city. It would explain why larger cities like Frederikshavn and Helsingør are so far off while smaller cities and settlements in the municipality are more accurate. It’s actually quite bad, for example (on expert) it has Helsingør being in the square west of Hellebæk when it should be in the square east of it.
Interestingly the pins are accurate on the Denmark largest cities quiz.