ImprovedErrorFrame lets you get more out of your error messages. It displays multiple errors and allows copying of error text.

With the new version of ImprovedErrorFrame, these errors are now queued up and can be viewed at your leisure with the click of a button. The error button is placed on the minimap and can be shift dragged to any other position around it.

Additional features include blinking notification, a notification sound, count of errors pending viewing and the ability to have the button displayed even when no errors are present.

Slash command help: /ief

Documentation: http://www.wowwiki.com/ImprovedErrorFrame