Event handler

I wanted to put some thing when receiving an application error. then the process needs to start form the begining. like m using browser some times due to browser issues one message is poping up with message as “IE is not responding please close the program and …” now i need to clik OK then need to start process again… please help

You can have a try-catch block and on a system exception you will restart your process. This can be easily implemented using state machines. You have an Init state and a Process state (and other states). All the processing is inside a Try-Catch and on catch you go back in the Init state, where you should kill used applications and start all over.

Install latest UiPath Studio 2018.1.x and you have the Robotic Enterprise Framework project which is design to do exactly what you want.
Also, you can learn more about the framework and how to use in the Academy Level 3 training.