HI arthur ,
it can be acheieved by CSS .
just take your Large image in a parent DIV , gve its a iD. then assign its css
now your smaller image will be in a div with style position:absolute .and give this
div top:200px nd left:200px; like this to make this in center .
your div-1a will be in div-1 as a child and you can locate this to center .
you can do this dynamically too from code behind .