This line will result in `NaN` in IE7-8, which _do_ support `obj.getBoundingClientRect()` but _not_ `window.pageYOffset` (`undefined`), ergo, e.g. `4 + undefined - 3` &rarr; `NaN`).  Additionally, the `doctype` value (or lack thereof) can also affect which property to query for the value (ugh!). :-1:

I believe the corrected version would be as follows:
```js
var pageYOffset = window.pageYOffset;
var topBorderWidth = document.documentElement.clientTop;
if (typeof pageYOffset !== "number") {
    pageYOffset = document.documentElement.scrollTop;
    if (!pageYOffset) {
      pageYOffset = document.body.scrollTop || 0;
      topBorderWidth = document.body.clientTop || 0;
    }
}
info.top = rect.top + pageYOffset - topBorderWidth;
```