Microsoft has very slick tool called Expression Web SuperPreview, I know that some people will say, we used to use another tool but what is the different here is it’s support for most browsers IE all versions and other browser Firefox, Safari, etc, it also open the site simultaneously with the 2 browser at the same time so you can recognize very fast what was the different, it’s also give you very helpful information about how the browser calculate positions an values, and above all this it’s free. And I think that’s exactly what we need.
You can download it from here, and to read more about this tool go to this site