Enable Quick Launch on a web part page.

To enable quick launch in a web-part page,

Step 1: open the SharePoint portal in SharePoint designer.

Step 2: Right-click the specific page(.aspx) that we want to enable the quick launch, and select "Edit File in advanced mode".

Step 3: Delete the style tag.


<style type="text/css">
body #s4-leftpanel {
display:none;
}
.s4-ca {
margin-left:0px;
}
</style>

Step 4: Delete the <asp:content>.


<asp:Content ContentPlaceHolderId="PlaceHolderNavSpacer" runat="server"></asp:Content>
<asp:Content ContentPlaceHolderId="PlaceHolderLeftNavBar" runat="server"></asp:Content>

Enough!!

Save the changes and preview the .aspx page in browser.