I am working with PrimeFaces messages, I want my whole page to scroll to top when p:messages is rendered.
Lets say that your button is causing the messages to appear.
XHTML
<p:commandButton value="Save" 
                 oncomplete="scrollToFirstMessage()" />
javascript
//javascript function which scroll to the first message in page   
function scrollToFirstMessage() {
     try {
        PrimeFaces.scrollTo($('.ui-message :first-child').eq(0).parent().attr('id'));
     } catch(err) {
       //No Message was found!
     }
  }
Hope this helps.
There are valid answers already that show how to scroll to the p:messages component, but they all require you to execute code in a backing bean. This requires you to do / call the same in each action. None show how to scroll to the messages component when it is rendered (updated).
You can implement a phase listener and check messages are present and if the messages component's clientId is present in the PartialViewContext renderIds:
These client identifiers are used to identify components that will be processed during the render phase of the request processing lifecycle.
Your listener can look something like this:
public class MessagesUpdateListener implements PhaseListener {
  private final String MESSAGES_ID = "yourMessagesClientId";
  @Override
  public void afterPhase(PhaseEvent event) {
    // Empty
  }
  @Override
  public void beforePhase(PhaseEvent event) {
    FacesContext fc = FacesContext.getCurrentInstance();
    if (!fc.getMessageList().isEmpty() &&
        fc.getPartialViewContext().getRenderIds().contains(MESSAGES_ID)) {
      RequestContext.getCurrentInstance().scrollTo(MESSAGES_ID);
    }
  }
  @Override
  public PhaseId getPhaseId() {
    return PhaseId.RENDER_RESPONSE;
  }
}
Make sure to register it in your faces-config.xml:
<lifecycle>
  <phase-listener>your.MessagesUpdateListener</phase-listener>
</lifecycle>
Tested with XHTML:
<h:form id="main">
  <p:messages id="messages" />
  <p:inputText id="text1" required="true" />
  this<br/>is<br/>a<br/>long<br/>page<br/>this<br/>is<br/>a<br/>long<br/>page<br/>
  this<br/>is<br/>a<br/>long<br/>page<br/>this<br/>is<br/>a<br/>long<br/>page<br/>
  this<br/>is<br/>a<br/>long<br/>page<br/>this<br/>is<br/>a<br/>long<br/>page<br/>
  this<br/>is<br/>a<br/>long<br/>page<br/>this<br/>is<br/>a<br/>long<br/>page<br/>
  this<br/>is<br/>a<br/>long<br/>page<br/>this<br/>is<br/>a<br/>long<br/>page<br/>
  this<br/>is<br/>a<br/>long<br/>page<br/>this<br/>is<br/>a<br/>long<br/>page<br/>
  this<br/>is<br/>a<br/>long<br/>page<br/>this<br/>is<br/>a<br/>long<br/>page<br/>
  <p:commandButton value="Update" update="messages text1"/>
  <p:commandButton value="No update"/>
</h:form>
To check for global messages, use:
fc.getMessageList(null).isEmpty()
See also:
Deprecated with PrimeFaces < 6.2
In you backing bean (that one which produces the messages), you should know when you render a p:message. If so simply execute this:
RequestContext.getCurrentInstance().execute("window.scrollTo(0,0);");
Update:
With the newer PrimeFaces versions (>= 6.2), the approach to execute Javascript on the client side is (by using x and y coordinates):
PrimeFaces instance = PrimeFaces.current();
instance.execute("window.scrollTo(0,0);");
To scroll to an element use the element's clientId:
PrimeFaces instance = PrimeFaces.current();
instance.scrollTo("myElementsClientId");
Find more information here:
Assign an ID to your p:message component
<p:messages autoUpdate="true" id="myMessage" />
Then, in your backing bean call RequestContext.scrollTo method:
in PrimeFaces >= 6.0:
PrimeFaces.current().scrollTo("myMessage")
in Primefaces < 6.0:
RequestContext context = RequestContext.getCurrentInstance();
context.scrollTo("myMessage");
which is deprecated in PrimeFaces 6.0