While excuting the page, it will go under the fallowing 
steps(or fires the events) which collectivly known as Page 
Life cycle.
Page_Init -- Page Initialization
LoadViewState -- View State Loading
LoadPostData -- Postback data processing
Page_Load -- Page Loading
RaisePostDataChangedEvent -- PostBack Change Notification
RaisePostBackEvent -- PostBack Event Handling
Page_PreRender -- Page Pre Rendering Phase
SaveViewState -- View State Saving
Page_Render -- Page Rendering 
Page_UnLoad -- Page Unloading

Init
loading
TextboxTextchanged
buttonclic
pageunload
pagedispose


The page is intialize the events,after that the page is 
loading,after that controls is rised after page unloading 
and pagedispose is removing the unnecessary objects

sorry, kavitha answer is wrong. There is no textchange when 
loading a page

init
load 
prerender
unload

Page_Init()-when page is first inistiated.
Page_Load()-when page is first loaded to server
Page_PreRender()-Few moment befor while html code is viewed 
to user.
Page_unload()-Page is unloaded from server memory

PreInit
 # Check the IsPostBack property to determine whether this 
  is the first time the page is being processed.

 # Create or re-create dynamic controls.

 # Set a master page dynamically.

 # Set the Theme property dynamically.
 
 # Read or set profile property values.

Init
  Raised after all controls have been initialized and any
skin settings have been applied. Use this event to read or
initialize control properties.

InitComplete
 Raised by the Page object. Use this event for processing
tasks that require all initialization be complete.

PreLoad
 Use this event if you need to perform processing on your
page or control before the Load event. 

Load
 Use the OnLoad event method to set properties in controls
and establish database connections.

LoadComplete
 Use this event for tasks that require that all other
controls on the page be loaded.

PreRender
 The PreRender event occurs for each control on the page.
Use the event to make final changes to the contents of the
page or its controls.

SaveStateComplete
 Use this event perform tasks that require view state to be
saved, but that do not make any changes to controls.

Render
 This is not an event; instead, at this stage of rocessing,
the Page object calls this method on each control. All
ASP.NET Web server controls have a Render method that writes
out the control's markup that is sent to the browser.

Unload
 This event occurs for each control and then for the page.
In controls, use this event to do final cleanup for pecific
controls, such as closing control-specific database connections.