No. In the Netherlands is not common to cycle on side walks. We have cycling lanes for that! Pedestrians and cyclists only meet at crossings. (The behaviour of cyclists in the big cities might be different though.)
You really don’t have to change your css. My personal website has been using roughly the same css for a decade. Why not?
Sure if you are a designer and want to follow trends, you’ll have to keep your css skills up to date. But for most websites, you can use css from a decade ago.