"Affects Version/s" is actually 184.108.40.206.
In my JSP, I have a <s:form id="some.complicated.value">
The HTML comes out at <form id="some_complicated_value">.
The dots in the id value silently get changed to underscores.
I did not find this replacement documented. Places I looked include http://struts.apache.org/220.127.116.11/docs/form.html and http://struts.apache.org/18.104.22.168/docs/tag-syntax.html and http://struts.apache.org/22.214.171.124/docs/form-tags.html .
Either fix the tags library to not silently rewrite attribute values. This is prefered by this bug reporter.
If a developer takes the trouble to nail down the id attribute to a specific value, that's the specific value that should be used.
Or else, if there is a reason for the rewrite, kindly document both the rewrite and the reason.