On the page https://os.mbed.com/docs/v5.6/reference/platform.html there is a sentence <<quote>> The Callback class manages C/C++ function pointers so you don't have to. If you are asking yourself why you should use the Callback class, you should read the [[https://os.mbed.com/docs/v5.6/reference/platform-overview.html#the-importance-of-state|Importance of State section]]. <</quote>> I think the link is pointing to a mid-point of an old version of the same page. In other words, it looks like * The link should be to https://os.mbed.com/docs/v5.6/reference/platform.html#the-importance-of-state * And the IDs (e.g. #the-importance-of-state) need to be added to the current page Some other pages link to the old version, too. And other IDs on the new page are broken, too - such as this one [[https://os.mbed.com/docs/v5.6/reference/platform.html#callbacks|Introduction to callbacks]], which is linked at the bottom of this page [[https://os.mbed.com/docs/v5.6/reference/callback.html|Callback]].