Image and bad display

Hi sir,

Excuse my english, i’m french.

I need your help : the “Image de une”, the picture which appear on first page isn’t always in a good format. Only one part of this image displays, like if the image was too big. And when I try too reduce the picture, nothing change. Even if I choose a very little resolution (100*42 for exemple), the picture is still giant and doesnt apppear good.

How can I resolve this matter ?

Thank u very much

Adevy.