It makes sense to consider the lowest number amongst browsers in fairly common use when considering the limit. IE7 may not be a "modern browser", but it's still

It makes sense to consider the lowest number amongst browsers in fairly common use when considering the limit. IE7 may not be a "modern browser", but it's still one in widespread enough use that we have to support it. (It was only in IE8 that MS bumped the limit to 6.)