I have a VF page that uses standard controller account. I want to modify the error message that is displayed when I type the wrong id (invalid) in the URL to avoid getting a message like this: (I want to still display the VFPage but with a custom message)

What is salesforce lighting exactly ,seems bit confusive .Can anyone guide me properly when to go for lighting and how to start learning to develope lighting component?

I want the visualforce page should be downloaded in excel format by clicking a button and also want to send parameter from one page to another page.

What is salesforce lighting exactly ,seems bit confusive .Can anyone guide me properly when to go for lighting and how to start learning to develope lighting component?

Difference between system mode and User mode?