1. Fix all markup errors (check in W3C validator).
2. Place CSS links before any scripts.
3. Move all scripts from onload, onmouseout and other attributes into script.
4. Move that script into separate file.
5. Do not use document.images, document.layers, document.forms. Use $() instead of document.getElementById(). Learn Prototype.
My Prototype 1.7 applications work fine in IE10 (as in all other Grade A browsers).