Within a PAL 16:9 video frame there are three distinct common title safety areas, they are:

16:9 Safe – basically the full width of the frame, suitable for 16:9 widescreen, and 16:9 letterbox viewing.
14:9 Safe – 14:9 is the middle ground between 4:3 and 16:9 – it is a slight crop, so the safe area is not the full width of the frame.
4:3 Safe – This means that graphics will remain fully visible after a 4:3 center-cut crop of the image. It is only around 65% of the frame width.

I’ve created a few PSD files that illustrate these safe areas (for PAL and HD frame sizes). They can be downloaded here framesizes.zip

These guides should conform to BBC and EBU recommendations. Other broadcasters may have their own specifications.