Looks cool doesn’t it. well here goes nothing..
to achieve the above you will need the following (click read more link..)

// the following code is for the hover over lookup window
function OnCrmPageLoad()
{
/*
Reference the to Lookup, Provide the lookup (control) id.
*/
var PrvToLui = new LookupPreview(”new_primarycontactid”);
/*
Add Account Preview Information [...]