To hide the “Recently Modified” list on the Quick Launch that appears on some of your pages
Do the following:
Go to the page where you wish to remove the section. Go into Edit Page mode and at the top of the page, click on “Edit HTML Source” under the “HTML” drop down menu.
At the top of the source code box, input the following:
Save the page and refresh and it should disappear.
Note: Another way to do this would be to enter that code into a notepad file. Upload the notepad file to your site and add a content editor webpart with that file linked into it. This is an easier way to apply it to multiple pages without having to modify your Master Page.