Know If a user has visited your site from a Blackberry

Question

I found this piece of code that can detect if a user has already visited your web page by injecting a hidden link into the DOM and checking if the color of it is the same as the one for visited links.

function hasLinkBeenVisited(url) {
            var link = document.createElement('a');
            link.href = url;
            document.body.appendChild(link);
            if (link.currentStyle) {
                var color = link.currentStyle.color;
                if (color == '#ff0000')
                    return true;
                    return false;
                } else {
                    link.setAttribute("href",url);
                    var computed_style = document.defaultView.getComputedStyle( link, null );
                    if (computed_style) {
                    if (computed_style.color == 'rgb(255, 0, 0)')
                    return true;
                }
                return false;
            }
        }

It works fine for desktop browsers, however it doesn't for Blackberry's. You guys know of a way of knowing?