Unity displays in the Inspector a help icon for every component. It’s this book icon with the ? symbol.
If you click the help icon, Unity opens a web-browser and opens the corresponding help page for that particular component.
Unless… there has no HelpURL been specified, like in the “Debug Draw Sample 1” Component in the above screenshot.
In this case, Unity tries to open a non-existent page, such as this one. I noticed this with so many Unity components that are provided through packages.
I suggest to display the help icon only, if there has been a HelpURL attribute provided. If it’s missing, either display the icon in an inactive (aka grayed-out) state or hide it entirely.
This prevents users from clicking this icon just to find there exist no documentation. Perhaps it also causes developers to be more aware where those HelpURL attributes are missing.