Problem jQuery UI tabs effect

Problem jQuery UI tabs effect

Hi,
I mounted a tabbed section on jQuery UI 1.2.7. I use ajax to call a file .html each time you click a tab.
Everything works correctly until you add an effect. To be more concise, everything continues to function well even after adding the effect, but now every time you press a tab or tabs, the browser goes to the top of the page.

JQuery function to which this happens is:

$(function() {
  $("#tabs").tabs({fx: {opacity: 'toggle', duration: 'fast'}});
  });


A demonstration of how the error: http://ico.comxa.com/tabs/ui_tabs1.html#tabs

If the function is simply the following, the problem disappears:

$(function() {
  $("#tabs").tabs();
  });


... and here the demo to work correctly, but without the effects applied: http://ico.comxa.com/tabs/ui_tabs2.html#tabs


Anyone knows how to solve this error?
Thank you very much.