/**
 * Whether browser is IE 6 or below.
 */
function isIe6() {
    var ie6 = false;
    var nAgt = navigator.userAgent;
    if ((verOffset=nAgt.indexOf("MSIE"))!=-1) {
        var fullVersion  = parseFloat(nAgt.substring(verOffset+5));
        if (fullVersion <= 6) {
            ie6 = true;
        }
    }
    return ie6;
}

/**
 * IE 6 and below doesn't support CSS fixed positioning so where necessary we change it to absolute amd position
 * it as an offset from the viewport.
 *
 * @param element element to position
 * @param topPercentage percentage offset from top as decimal
 */
function checkFixedPositioning(element, topPercentage) {
    if (isIe6()) {
        var offsetArray = document.viewport.getScrollOffsets();
        element.style.position = 'absolute';
        element.style.top = offsetArray[1] + (document.viewport.getHeight()*topPercentage);
        var viewDisabled = $('viewDisabled');
        viewDisabled.style.position = 'absolute';
        viewDisabled.style.top = offsetArray[1];
        viewDisabled.style.width = document.viewport.getWidth();
        viewDisabled.style.height = document.viewport.getHeight();
    }
}


/**
 * Center's the specified element in the middle of the viewport.
 *
 * @param element element to position
 */
function centerInViewport(element) {
    var prototypeElement =  $(element);
    var offsetArray = document.viewport.getScrollOffsets();
    var left = ((document.viewport.getWidth()-element.getWidth())/2)+offsetArray[0];
    element.style.left = left + "px";
    var top = ((document.viewport.getHeight()-element.getHeight())/2)+offsetArray[1];
    element.style.top = top + "px";
}