Hiding header and Sidebar in Salesforce

some times we need to hide header and sidebar of a visualforce page or standard layout.

we can do it by writing showheader = "false"  and sidebar = "false" in the visualforce page.

for example 

<apex:page controller = "TestController"  showheader = "false" sidebar = "false">

   // your information 

</apex:page>

How can we hide in header and sidebar standard layout ?

ans- Salesforce is user friendly language, There is also a feature available so called "Enable Collapsible Section", By using this we can only hide sidebar
you can go in this way Name-->set up-->customize--> user interface--> checked the check box "Enable Collapsible Section", after that you can show or hide sidebar.

If someone wants to hide both sidebar and header of standard layout, then how will we do it? 

Ans- It is very simple, just append "isdtp = vw" at end of link in the URL, you will see the magic.

Also you can write this in apex code.for example

PageReference samepage= new PageReference('/apex/pagename?recordid&isdtp=vw);

For testing you can write "isdtp = vw" in the any standard layout, It will automatically hide header and sidebar, Try It.