How to center a picture using span or div?

[am omid]

hello
excuse me. i dont speak english very well.
i want to know that how do i take my banner picture in top and center of my web?
<span style=" ? " > or <div ? >
please ask me

[hellodipak]

<div style="text-align: center;"><img src="imagepath/imagename.jpg" /></div>