Which web technology to learn for an experienced C++ developer?
I expect this question to be closed as being subjective.  But, I'll put in my 2 cents.
JSP would likely dovetail well with J2EE.  (I've heard that it can be a bit rigid, but I have no experience to provide any insight on the matter.)
PHP is a good candidate, because it's popular.  You can find a lot of info on the web.
Python isn't as popular for webdev, so finding examples won't be as easy.
I also second Dave Markle's opinion.  If you want to learn webdev, HTML, CSS and JavaScript will be crucial as well.  You may never want to be a front-end developer, but you can't get away from dealing with those technologies at some point.
Friends, 
I've got some exp in c++ and now kind of starting my way to J2EE (to survive:))). Meanwhile, I've got a plan to venture in to a web portal my own. But with very little experience in web technology, I'd need to start from scratch. I'm little confused on which way to go and I'm here. 
PHP, Python or JSP, considering the fact that, anyway I've got to learn J2EE at my work.
Would that be worth to learn PHP or Python to develop a portal which I expect to get 80-100K 
hits per day "IF" everything goes well OR jsp would be sufficient? 
Many thanks