See your markup in context with X-Ray
A neat addition to the list of Firefox extensions that really help make a web developer’s job a bit easier is X-Ray.
Stuart Robertson’s X-Ray Firefox extension enables you to see the markup of a page without viewing source, which can be really helpful when debugging your work. It’s also both fun and educational to use X-Ray to explore the markup used on other people’s sites.
X-Ray is very revealing, so better make sure your markup is in perfect shape!