On the Internet there are lots of sites on Morse Code, some good, some bad and some very bad, the latter want to be avoided. So how do we identify which is good and which is bad? I would just say watch our for the person who has just managed to get his 5wpm certificate and put up a website on how to learn Morse. Experienced operators have put up some good websites and hopefully I will be listing then in the Links Section. If you find a site that would be suitable for listing, please contact me and I will have a look at it.
If the character speed is less than 12wpm, avoid it as you will not be able to learn Morse code as a reflex action thus making it harder for you to improve your proficiency. Find out what David Finlay N1IRZ has said on this subject,
These should be avoided at all costs, although they can be helpful at slow speeds, most learners find that they peak at 10wpm and find it very difficult to progress further.
They are only useful if you do not want to learn Morse code, but have no value if you want to learn and use Morse code, except for checking your own sending proficiency.