download image from an asp.net page

hi
i want to download image from an asp.net page.
there is one option that we have do
<a href="imagepath" target="_blank" >Download</a>
with this image open in new window and from there we can save image through saveas option.


but i want download image not with save as option.
foe eg. in gmail  attached  images can be downlaod. nd i want this option.
thanx

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