1)HTML is a web design language and CSS is a presentation, styling and formatting language.
2)HTML can control the contents of the page while CSS doesnot control the content of the page.
3)In CSS,we can reduce the length of the code and increase effectiveness compare to HTML.
4)HTML is responsible for the construction and the total output, of the page.
while CSS does not create anything instead it decorates,aligns and positions elements in HTML.

Any other ideas will be appreciated.......................