I was able to get my page to validate as xhtml 1.0 transitional, but not xhtml 1.0 strict.
I had the same problem on my blog. I input the html code directly into the database via phpMyAdmin. This solved the problem of the textarea tag. I think wordpress doesn’t let you include the code as is because it isn’t valid xml. I don’t really care because it is just a static page and not a post.
If you have some javascript that validates the form, you will have to include it somewhere else or it won’t work. I just put it in the header file.
Check it
