Tryit Editor v1.8

Source Code:
<!DOCTYPE html> <html> <head> <style> body {counter-reset:section;} h1 {counter-reset:subsection;} h1:before { counter-increment:section; content:"Section " counter(section) ". "; } h2:before { counter-increment:subsection; content:counter(section) "." counter(subsection) " "; } </style> </head> <body> <p><b>Note:</b> IE8 supports these properties only if a !DOCTYPE is specified.</p> <h1>HTML tutorials</h1> <h2>HTML Tutorial</h2> <h2>XHTML Tutorial</h2> <h2>CSS Tutorial</h2> <h1>Scripting tutorials</h1> <h2>JavaScript</h2> <h2>VBScript</h2> <h1>XML tutorials</h1> <h2>XML</h2> <h2>XSL</h2> </body> </html>
Result:
W3Schools.com - Try it yourself