Amazon has a history for being awful with making web pages. I had to peruse the Amazon HTML code once for a research project not long ago, and their code was littered with issues, including duplicate id.
Their UX and even UI is rotten beyond belief.
Really? I've been consistently amazed with Amazon's web UI. It works perfectly no matter if you have javascript on or off, no matter what browser. I bet I could order in lynx if I wanted to. Almost no other large site does it as well.