How to get the Microsoft CRM “Closed Activities” Nav Bar Link Back (if you delete it)

Just export the solution of entity and add following relationship

<NavBarByRelationshipItem RelationshipName="Contact_ActivityPointers" Id="navActivityHistory" TitleResourceId="Tab_Label_History" Icon="/_imgs/ico_18_history.gif" ViewId="21E2B905-6FDB-470d-8517-AD69B4C01268" Sequence="20" Area="Info">
<Privileges>
     <Privilege Entity="" Privilege="ReadActivity" />
</Privileges>
<Titles>
<Title LCID="1033" Text="Closed Activities" />
</Titles>
</NavBarByRelationshipItem>

Here I have set the example of contact entity.

Default Activity ‘Filter on’ to ‘All’ Dynamics CRM 2011 UR12

//default the Activities 'Filter on' to 'All' for Account and Contact for rollup 12 

function filterAllActivities() {
    document.getElementById("navActivities").onclick = function () {
        Mscrm.Details.loadArea(this, "areaActivities");
        document.getElementById("areaActivitiesFrame").onload = function () {
            var entityName = Xrm.Page.data.entity.getEntityName();
            var entity = entityName.charAt(0).toUpperCase() + entityName.substr(1);
            var doc = this.contentWindow.document;
            var filterOn = doc.getElementById("crmGrid_" + entity + "_ActivityPointers_datefilter");
            filterOn.value = "All";
            var evt = document.createEvent("HTMLEvents");
            evt.initEvent("change", false, true);
            filterOn.dispatchEvent(evt);
        };
    };
}