Break point on opera Dragonfly
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In opera dragonfly, we have 2 button:
1. Break on first statement of a new script
pauses the execution each time a new script is loaded and the first statement is evaluated. 

2. Break on error, but in dragonfly it's called "Show parse errors and break on exceptions"
Description: 
It is possible to get Opera Dragonfly to stop execution when a parse error occurs. Enabling the last button in the Scripts toolbar will stop JavaScript execution at the line where the parse error occurred and highlight it in the gutter in a similar manner to breakpoints. The same button will also stop execution when an exception is thrown.

What is it the second break "Show parse errors and break on exceptions" ? 
When I load gmail page it will stop execution. It's the sam like pause on all exceptions?
Thanks.