3.5.5.2 Auto-Show Parse Messages

If this option is selected, when you start a render, a small version of the message window will be opened at the bottom of the edit window. You can resize this window vertically using the mouse. To close it, just hit ESCAPE.

Note that unless you have 'Auto-Load Error File' selected, the message window will remain visible upon a parse error (so that you can see it without switching windows). If the render completes successfully, the message window will close.