In my application, we're very dependent on a service to provide some information that the user can interact with. It's possible that the service could be down, or in some invalid state to where any usage of it cannot occur. I'm curious as to how I should display said scenario to an end-user if they are trying to retrieve data from it.
Assuming a rectangular grid is showing the results in a column/row fashion, I'm thinking of adding an exclamation point at the top right corner, above the grid, if an error occurs during service access. Perhaps with a tool tip that when hovered over with a mouse would display the error message.
I'd like it to be obvious enough that something occurred, but not too obvious to where it clutters the UI.