How to Get Account related Contact IDs in List View

[ND]

Hello

I have two problems.

1) I created a custom button for Lead Tab that returns selected Lead ids using {!GETRECORDIDS( $ObjectType.Lead)}; in JavaScript onClick. The java script further calls an apex web service. This works fine.

Now I want to implement same functionality for Account Tab but in this case I want all Contact IDs for selected Account rather than selected Account IDs. It means i want all contact ids for selected accounts.

2) The Custom button mentioned above is available only in List View. 

 The Problem is List View is not default view when user launches Standard or Custom tab and one have to click on 'Go' button to launch the List View to see the custom button placed on it. So how can I set List View as default view while user clicks on Tab so that custom buttons can be directly show to user.

Thanks in advance