How to hide the Left navigation bar or Quick launch Sharepoint 2010

To hide the left navigation bar\ Quick launch , you can add the follow the below mentioned steps.

Site Actions

Edit Page 

Add a webpart

Add Content Editor Webpart

Modify shared webpart - Edit the Source Code and paste the below code in Source code .

<Style>
body #s4-leftpanel
{
display: none;
}
.s4-ca
{
margin-left: 0px;
}
</style>

Select Ok. Then from the Appearance Section Hide the webpart - Click Apply Ok. Exit Edit mode.

Hope this helps