jQuery UI dialog positioning

As an alternative, you could use the jQuery UI Position utility e.g.

$(".mytext").mouseover(function() {
    var target = $(this);
    $("#dialog").dialog("widget").position({
       my: 'left',
       at: 'right',
       of: target
    });
}

Thanks to some answers above, I experimented and ultimately found that all you need to do is edit the "position" attribute in the Modal Dialog's definition:

position:['middle',20],

JQuery had no problems with the "middle" text for the horizontal "X" value and my dialog popped up in the middle, 20px down from the top.

I heart JQuery.

After reading all replies, this finally worked for me:

$(".mytext").mouseover(function() {
    var x = jQuery(this).position().left + jQuery(this).outerWidth();
    var y = jQuery(this).position().top - jQuery(document).scrollTop();
    jQuery("#dialog").dialog('option', 'position', [x,y]);
});

Taking Jaymin's example a step further, I came up with this for positioning a jQuery ui-dialog element above the element you've just clicked (think "speech bubble"):

$('#myDialog').dialog( 'open' );
var myDialogX = $(this).position().left - $(this).outerWidth();
var myDialogY = $(this).position().top - ( $(document).scrollTop() + $('.ui-dialog').outerHeight() );
$('#myDialog').dialog( 'option', 'position', [myDialogX, myDialogY] );

Note that I "open" the ui-dialog element before calculating the relative width and height offsets. This is because jQuery can't evaluate outerWidth() or outerHeight() without the ui-dialog element physically appearing in the page.

Just be sure to set 'modal' to false in your dialog options and you should be a-OK.