http://download.mcneel.com/s3b/mcneel/grasshopper/1.0/sdk/en/GrasshopperSDK.chm (I know this one can be compiled from within GH, just FYI)
Both of these links throw a Not Found error here.
Could you tell us where you found those links so that we can fix the source of the issue?
This one has changed several times (if you had it stored as a bookmark). It is now:
https://developer.rhino3d.com/api/RhinoCommon/html/R_Project_RhinoCommon.htm
Yeah, I had it stored as Bookmark, don’t really know where I got it from.