Are Your Error Messages Easily Understood?

As I was finishing installing Microsoft Office on my home PC, I was presented with this alert:

Microsoft Office installation alert message
Microsoft Office installation alert message

What does this even mean?! What are the consequences if I say yes?

Web application error messages and alerts are often equally badly written because all too frequently they are left to developers to write or the default ones that come with the software are used.

This is not a good thing. Error messages and alerts should be treated as part of the UI along with the more visible components of the application.