In SharePoint 2010, we had a method for hiding the Quick Launch on a SharePoint site to clean the interface look and feel if you are building out a site which doesn’t benefit from having a quick launch.
In SharePoint 2010, we did this using a Content Editor Web Part and editing the source HTML code of the Web Part to include some custom CSS however in SharePoint 2013, those same CSS Selectors don’t work because Microsoft have changed the names of some of the CSS Selectors. In SharePoint 2013 to hide the Quick Launch we now do it using the following approach.
Add a Script Edit Web Part from the Media and Content category.
Once you’ve added the Web Part, Edit the Web Part and add the following code snippet.
<style>
#contentBox {margin-left:0px}
#contentRow {margin-left:19px}
</style>
If you want to take this a step further and hide the top navigation links, you can add an additional line of inline CSS code to achieve this. Edit the Web Part and add the following line in addition to the code already specified for the Quick Launch.
.ms-core-navigation {display:none}