How can I hide all errors from an Eclipse project?

I don't know if you can hide all the errors but you can

• limit the number of reported problems in Preferences -> Java -> Compiler -> Building, or
• exlude all the files from your build path folder (Java Build Path -> Souce -> Select source folder and Edit... -> Enter folder name and press Next -> Add '**' as Exclusion pattern)

Just disable JavaBuilder in Properties -> Builders. Sometimes after disabling JavaBuilder error status is not updated (they are still visible). In that case do the following:

1. In Properties -> Java Build Path -> Source remove source folder(s)
2. Clear project using Build -> Clear...
3. Disable JavaBuilder as described above
4. Add source folder(s) again

That way you should not be irritated with error messages any longer, but retaining all the possibilities to navigate by ctrl+click, search references etc.