Is there anyn way to fix the size of a popup window to auto?

Currently I'm doing a project in which i needs to collect data from a user and need to generate a PDF based on the user entered data. Before generating the PDF, there should be an option to display the preview of the same PDF. so i used the below codes:

$("#btnPreview").click(function () {

var data = UserData();

model = data.modelnew;

FamilyArray = data.familynew;

$.ajax({

url: "/CareApplication/Create",

type: 'POST',

contentType: 'application/json',

async: false,

data: JSON.stringify({ model: model, Family: FamilyArray, flag: "1" }),

success: function (data) {

var myPos = { my: "center top", at: "center top+100", of: window };

var $dialog = $('

.html('')

.dialog({

autoOpen: false,

modal: true,

height:650,

width: 1200,

title: "Preview",

position: myPos,

});

$dialog.dialog('open');

}

});

window.scrollTo(0, 0);

});

here i have fixed the size of the popup window(height:650, width:1200), due to this the size of the popup window varies for different browsers. So I cant close the popup window. my question is that Can i fix the size of the pop up window to automatic? This popup window should display on the same page.