Web Dynpro error log location

I'm pretty new to Web Dynpro and have a few questions regarding the location of the different error log.

1. Sometimes the web dynpro IDE prompt up saying "please check the error logs for details". Where is the error log located?

2. After i deployed and run the Web Dynpro application, there is a "Red Exclaimation" picture and the bottom of the web page. Where to find this error log?

3. Where is the error log for run time error, eg, NULL POINTER exception etc ?

Any help would be much appreciated. Thanks.