javascript get style pixel value in ie6 and ie7

Computed vs Cascaded Style

var PIXEL = /^\d+(px)?$/i;

function getPixelValue(element, value) {
    if (PIXEL.test(value)) return parseInt(value);
    var style = element.style.left;
    var runtimeStyle = element.runtimeStyle.left;
    element.runtimeStyle.left = element.currentStyle.left;
    element.style.left = value || 0;
    value = element.style.pixelLeft;
    element.style.left = style;
    element.runtimeStyle.left = runtimeStyle;
    return value;
};

References

1. Computed vs Cascaded Style