Answer by Houdini Sutherland for Bootstrap modal appearing under background

CAREFUL WHEN APPENDING TO THE BODY!

This will definitely get that modal from behind the backdrop:

$('#myModal').appendTo("body").modal('show');

However, this adds another modal to the body each time you open it, which can cause head aches when adding controls like gridviews with edits and updates within update panels to the modal. Therefore, you may consider removing it when the modal closes:

For example:

$(document).on('hidden.bs.modal', function () {
        $('.modal').remove();
    });

will remove the the added modal. (of course that's an example, and you might want to use another class name that you added to the modal).

And as already stated by others; you can simply turn off the back-drop from the modal (data-backdrop="false"), or if you cannot live without the darkening of the screen you can adjust the .modal-backdrop css class (either increasing the z-index).