It is possible to change style of the notebook. This includes amongst other font styles, colors and size. To achieve this, simply specify the style using CSS or HTML within a markdown cell or in a raw cell. The style won't show up until stored as .html or opened in nbviewer.
The following is an example of an header from a notebook on numfys.net:
<style> @import url(https://www.numfys.net/static/css/nbstyle.css); </style> <a href="https://www.numfys.net"><img class="logo" /></a> # Orbits in the Schwarzschild Geometry (General Relativity) ### Examples - Astrophysics <section class="post-meta"> By Eilif Sommer Øyre, Jonas Tjemsland and Jon Andreas Støvneng </section> Last edited: February 23th 2018 ___
The code is inserted directly into a markdown-cell. The style of the notebook is specified between <style> and </style>. In our case, we link to a css-file stored on the website. Alternatively, the content of the file can be inserted directly.