If you don't bother about adding javascript, here is a jQuery script that will add a margin to the ul that overlaps the image so all the list items remain aligned, and then assigns a negative margin to the li's that doesn't overlap.
$(function(){
//Define a context so we only move lists inside a specified parent
var context = $("#test_div");
//Build a list of images position a size
var imgRects = [];
var imgs = $("img.left", context);
imgs.each(function(i){
var pos = $(this).position();
pos.right = pos.left + $(this).outerWidth(true);
pos.bottom = pos.top + $(this).outerHeight(true);
imgRects.push(pos);
});
//Process each li to see if it is at the same height of an image
var lis = $("li", context);
lis.each(function(i){
var li = $(this);
if(li.parent().css('marginLeft') != "0px"){
return; //Already moved
}
var top = li.position().top;
for(var j in imgRects){
var rect = imgRects[j];
if(top > rect.top && top < rect.bottom){
li.parent().css('marginLeft', rect.right);
return;
} else if(li.parent().css('marginLeft') != "0px"){
li.css('marginLeft', -1 * rect.right);
}
}
});
});
I've tested with your demo page and jQuery 1.3.2 and it works on FF3.5 and IE8 because the image is on top of the document. If the image appears in the middle of a ul, the firsts li's will remain padded. If you need to correct this issue leave a comment and will try to update the script.