jQuery Grid Plugin - jqGrid

Hi, there. In fact, I am not sure whether it is a bug or not.

the css of body is like this:

body{

  width: 700px;
  margin:0 auto;

}

so the body is displayed in center screen.

Then I put a jqgrid in the body. Everything is ok.

But when I click the add or edit navbuttons, the body is displayed in the left of the browser. It only occurs in IE6, not in FF.

Please give me some advice to fix it.

Thank you.