how to disable page with opacity when simple div popup is shown .

You can do it.
Just add one id attribute to the div or table you want to change the opacity or disable, when popup is shown.
Then change its opacity according to popup's visibilty.
Something like below...

<div class="register" id="totalTable">
div contents goes here...
</div>
<div id="divMakeModelExist" runat="server" style="top: 300px; left: 600px; display:none; position:absolute;opacity: 0.7;"> Make doesnt exist ??
</div>

Now when you call the function to show popup like below...

$("#divSectionExist").show();

after this add codes to change the opacity of that div like...

$('#totalTable').css('opacity', '0.20');
$('#totalTable').css('filter', 'alpha(opacity=20)');
$('#totalTable').css('filter', '"alpha(opacity=20)"');

Here three lines of codes are written for cross browser compartibility.
Now when you call the function to hide that popup like below...

$("#divSectionExist").hide();

after that add codes to again change the opacity and come back to normal like...

$('#totalTable').css('opacity', '1');
$('#totalTable').css('filter', 'alpha(opacity=100)');
$('#totalTable').css('filter', '"alpha(opacity=100)"');

Refer one article Creating Popup Dialog Windows using JQuery[^] to know in details about the concepts.
You can Download Source Code[^] and check this demo[^] provided in that article.

Thanks...
Happy coding...:)