Problem with my JVC AV-28R25EK, maybe??!

I was wondering if anybody could help me?

I have a JVC AV-28R25EK 28" widescreen TV. When I watch widescreen DVD's and things like that, the tv displays a black strip across the top and the bottom of the screen. I realise that it is suppose to do this, but they seem a bit uneven. The best way I think I can describe it is;


____________________
____________________

Picture

____________________

____________________

The bottom black strip is a lot wider than the top black strip.
I don't know if this is a problem, as I see all the picture anyway, but I'm just worried that when am watching something non-widescreen, I am missing out something on the top.

Is this normal, or has something gone from with the picture alignment on my TV?

Any advice would be greatly appreciated.

Cheers!