What is trouble shoot if you are unable to open Sharepoint Farm or if the page is rendering 503 error code?

The work around for this is as follows: 1.We have to navigate to IIS under Administrative Tools in ControlPanel. 2.Than,we have to navigate to Application Pools->Sharepoint Central Administration v4.And click on Advanced Settings,a pop up will open in which you can view Identity under Process Model. 3.By clicking on the Identity,you can set your username and Password.After changing them,if you refresh the Sharepoint Page,you can view the page which the error won't be rendering again.