Remove Recently Modified from Quick Launch

If you are working in SharePoint 2010, you may find that your quick launch creates a section called 'Recently Modified'. This section is great for showing what recently changed on the site. However, it is not always needed. 

To remove this section from the quick launch:

1. Add a Content Editor Web Part (CEWP) to the page 
2. Edit the web part's source code 
3.  Add the following code:  

      <style>

      .s4-recentchanges{

       display:none;

      }

      </style>




The recently modified section will be removed. 




Source: http://thechriskent.com/2012/07/05/hiding-the-recently-modified-section-in-sharepoint-2010/