jQuery Ajax-更新div

I'm trying to make update div block after jQuery ajax succesfull request, this is works but all blocks dublicates (picture1), in picture 2 is shown how it looks after refreshing page with browser.

To update block I'm using function:

function async_get(addr,func) {
    $.ajax({
       url: addr,
       async: false,
       success: func
    });
}

and it's called like this:

async_get(
  'http://localhost/getfreelance/welcome', 
  function (data) {
     $('#header').html(data);
  }
);

Any solutions? :)

Picture 1: http://postimage.org/image/uxghnpgfb/

Picture 2: http://postimage.org/image/wj0v02md7/

You didn't understand, i need to update/refresh div block when ajax request is success, instead of your function fffsuccess() i'm using: 'function async_get(addr,func) { $.ajax({ url: addr, async: false, success: func }); }' and my #header div updates but it dublicates data.

html:

<div id="YourImgDivID"></div>

function:

function fffsuccess(){ 
    alert('success!');
    $("#YourImgDivID").html('<img src="image1.png">');
}

function ffferror(){ 
    alert('error!');
    $("#YourImgDivID").html('<img src="image2.png">');
}

use:

$.ajax({
    url: 'ajax.cos.php',
    type: 'post',
    async: false,
    success: fffsuccess,
    error: ffferror
});

P.S. you can replace

$("#YourImgDivID").html('<img src="image2.png">');

to:

$("#YourImgDivID img").attr('src', 'image2.png');

or

html to:

<div id="YourImgDivID"><img id="YourImgID" src="image105.png"></div>

jQuery to:

$("#YourImgDivID img#YourImgID").attr('src', 'image2.png');

whatever