I received a message about my grandfather and his marriage. There were several spelling errors of names. How do I correct errors in your database?
Whether and how you can correct an error rather depends on which specific part of FamilySearch's (enormous) database you're talking about.
If the error is in the shared, collaborative Family Tree, then you can edit nearly everything. For most corrections, it's best to go to the relevant profile's Details page and use the "edit" (pencil) button on the erroneous conclusion.
If the error is in the indexing of a historical record, then the availability of user corrections depends on the collection. Some fields of some indexes are correctable, using the "Edit" button in the middle of the top black stripe of the individual index entry page.
If the collection or field is not correctable, then you can console yourself with the fact that the index is not the data. It is merely a finding aid for the data, and given that you'd like to make a correction, it has by definition served its purpose: you found the record.
If the genealogical information is wrong it tends to be propagated by other researchers which over time will result in more bad information being out on the internet. At present Family Search is sending me information on a supposed 2nd great grandmother that is incorrect because she is not in my tree at all. Apparently I can't edit it so do I ignore it and let it continue to mess up any future researcher's work? Totally frustrating!