As much as developers and designers around the world would like IE6 to just die already, the reality of the Web is the same as it has been since nearly the beginning—not all browsers are created equal, and we have to test our sites across as many platforms as possible.
If you’re at a company with a QA department that covers all the bases, they’ll test your work before it goes out, but by the time it’s in QA, you’re in damage control mode, and it’s too late to really design across browsers. What’s more, if you’re a freelance designer or a small shop, you may not even have a QA team with multiple environments at the ready.
NetRenderer is a public service by German IT service provider GEOTEK Datentechnik. It allows designers and developers on Macintosh and Linux systems to see their sites rendered by Internet Explorer 9, 8, 7, 6, and 5.5.
Another useful feature is the Difference Mode:
A unique Mixed Overlay and Difference Mode helps to identify even subtle positioning discrepancies between IE6 and IE7 by adding or subtracting both images and displaying the result. Screenshot images are always 100% original size and a ruler marks maximum usable viewing widths on 800×600 and 1024×768 displays, taking into account the browser scrollbar.
Don’t wait until you’ve finished designing your site to check cross-browser compatibility.