fixed width sites prone to shifting around on page load from scrollbar?

[sross]

It seems all vbull fixed width sites do this but only on some pages.. for example on this site in threads list i can hit refresh and the site stays the same but in the forums list it jerks when the scroll bar appears. Is there a workaround for this? I find it very distracting on my forum. Would forcing a scroll bar to load on each page do it? This seems to happen on short or tall pages.. If there is code to force a scroll bar such as :

  html {
    overflow-y: scroll;
  }

or

html, body {
height: 100%;
margin-bottom: 1px;
}
or
html {overflow-y: scroll;}

Where would i put this code in the vbull style? Thanks!