This is just a suggestion. I validated a page and was missing <li> tags in a <ul>. The validator  recommended that I had rearranged tags. The code was <div><ul></ul></div>. It recommended that somewhere in my document I had reversed end tags as in </div></ul>. I searched the document for ten minutes for the rearranged end tags. I then used Tidy, it showed me where I missed the tags. After thumping my forehead a couple of times for looking right over it I proceeded to validate the page. I was just shocked that the validator had suggested rearranged tags and not the missing <li> tags. Maybe that will help some one else out in the future?