function chkUserName()
{
stTimeout("document.getElementById('dSUpUName').focus()",100);
}
this is working fine.butwhy do we need that setTimeout function………

html page:

User Name

Password

what i trying is chacking the username when user moves for the username field.for that i want to raise the onblur event handler with addEventListner or attachEvent,just like this.

function loadEvents()
{
if(document.addEventListener)
{ document.getElementById("dSUpUName").addEventListener("blur",chkUserName,false);
}
else
{
document.getElementById("dSUpUName").attachEvent("onblur",chkUserName);
}
}
function chkUserName(e)
{
//first i want to keep the foucs in the same element.for that i am using this.focus().
this.focus();
//return false;(first i tried like this to prevent default action)
preventDefaultAction(e);
}
function preventDefaultAction(e)
{
e = e ? e : window.event;
if(e.preventDefault)
{
e.preventDefault();
}
else
{
e.returnValue = false;
}
}

and one more important thing is when we attach that event handler to the html tag it is working fine in all browsers

for this the javascript code is

function chkUserName()
{
document.getElementById('dSUpUName').focus();
return false;
}

the problem occurs when we are trying to hadle the onblur event from javascript.
and why the onblur event behaves so special when compared to other events.

please help me…

But preventing the default action depends on the element and the event. For instance, if you have a link:

<a href = "http://blog.stchur.com" rel="nofollow">stchur blog</a>

And in a 'click' event handler for that link, you prevent the default action, you are telling the browser "don't do the think you normally do when a click occurs on a link." In other words, you're telling the browser NOT to navigate to the href of that link (which would be its default action).

In your case, you are trying to prevent the default action of a 'blur' event on some element '#dSUpUName' (which I have no idea what type of element that is because you haven't told us). But in any case, I'm not sure that preventing the default action of a 'blur' is something the browser will let you do. I would also question if you really want to do it — it could make for a really lousy user experience.

You may be able to re-focus #dSUpUName from within a 'focus' event handler of ANOTHER element. In that case, you might want to wait until the user gets all the way through the form and focuses on the submit button. At that point, perhaps you could validate the form and then call .focus() on the first invalid element you find.