In Salesforce when we hover on a lookup field on a record detail page, we can quickly view some information related to the lookup record in a little popup window. That popup window is called mini page layout.

A mini page layout contains a subset of the items in an existing page layout. Sometimes we need to customize the mini page layout as per our requirement.

Here is the mini page layout of Account object, which is showing in Contact record details page.

Follow below steps to edit mini page layout:

• Go to Setup || Customize and choose a Standard object, or Go to Setup || Develop || Objects and choose a custom object.
• Select Page Layouts, and choose a page layout name.
• Click Mini Page Layout.

• Select which fields and related lists will be displayed for this type of record in the mini view.

• Updated Account object mini page layout view on Contact details page.

Note:

• There are field that we cannot remove (Like – object name, Parent Account for account object) To hide this, we can use Field Level Security, but of course field will not be visible anywhere, like: page layout, report, etc.
• There are field that always shown, example in User object, it will always show Title, Email, Phone, Manager.
• We cannot choose related objects for the Close Case Layout or the Log a Case Page and View Cases Page layouts on the Self-Service Portal.