What I want is like stack overflow. User can HTML format their text input, and the page should be rendered exactly in the same way,
I use the wmd.js to stor
wmd.js
For simple HTML formatting, use {{something}}. And the Javascript way is,
{{something}}
If that {{something}} itself contains the HTML tags, then {{something|safe}} itself should work unless you have {% autoescape on %}. For more filtering and formatting refer Built-in template tags and filters.
{{something|safe}}
{% autoescape on %}