In jQuery how can I set "top,left" properties of an element with position values relative to the parent and not the document?

Question

To set the position relative to the parent you need to set the position:relative of parent and position:absolute of the element

$("#mydiv").parent().css({position: 'relative'});
$("#mydiv").css({top: 200, left: 200, position:'absolute'});

This works because position: absolute; positions relatively to the closest positioned parent (i.e., the closest parent with any position property other than the default static).

$("#mydiv").css('top', 200);

$("#mydiv").css('left', 200);

You could try jQuery UI's .position method.

$("#mydiv").position({
  of: $('#mydiv').parent(),
  my: 'left+200 top+200',
  at: 'left top'
});

Check the working demo.

I found that if the value passed is a string type, it must be followed by 'px' (i.e. 90px), where if the value is an integer, it will append the px automatically. the width and height properties are more forgiving (either type works).

var x = "90";
var y = "120"
$(selector).css( { left: x, top: y } )        //doesn't work
$(selector).css( { left: x + "px", top: y + "px" } )        //does work

x = 90;
y = 120;
$(selector).css( { left: x, top: y } )        //does work

Code offset dynamic for dynamic page

var pos=$('#send').offset().top;
$('#loading').offset({ top : pos-220});