I want to call big image on mouse over of small other image

I want to show small image and on mouseover i want to show other big image on small image (not as tooltip or not zoom).

Suppose, my small image is in left-top then big image and small image's left top should be same.

Same way, if small image in right-bottom of page then big image's right-bottom should be same as small image's right-bottom.

(You may have seen that ads by kontera and adbrite text rollover ads, those ads will be displayed in always in screen. if text is at right border of screen then ads will be in left side and same for all sides.)

Please let me know is there any jquery/dojo/scriptaculous script which can do this?

In jQuery you can use the hover() function to simply change the "src" attribute of the <img> tag to show the big image. This requires separate thumbnail and big images. You could also change the width and height attributes but that will look terrible.