Put javascript and css inline in a single minified html file to improve performance?
Concatinating your CSS and JS files into one file will reduce the number of requests and make it load faster. But as commented, it won't make much sense unless you have a one-page site and the load time of that page is very critical. So you're better off to separate CSS from Javascript in my opinion.
Here's a book where you can learn more about the topic:
this tools maybe help you. Turns your web page to a single HTML file with everything inlined - perfect for appcache manifests on mobile devices that you want to reduce those http requests.
https://github.com/remy/inliner
This is not a good idea for the following reasons:
You will not enjoy the benefit of cache
You will load unneeded resources in all of your pages
You will have a hard time while developing your website because of large files with unrelated code branches
If you work in a team you will have to work with your teammates on the same files always, which means that you will have a lot of merge conflicts.