Below are two examples of using a personal style in a browser. They follow ‘before & after’ order.
Design Week’s new website has a very strong header, uselessly stuck to the top of your window, that disrupts viewing and reading and ‘blocks’ the content to have better impact. Also makes my head squint.
Below an example after adjusting styles in the browser. The content stands out and can be easier focused on.
Following similar example with a video post.
Below a sticky header done right – gives access to related sections without disrupting content experience.
Another example. Wikipedia’s outdated design makes long articles pain to read – font is too small, lines are too long.
A small tweak – applying a custom style to body text (<p> element) makes it much easier to read.
Below a popular browser stylesheet editor. Styles can be applied to the whole domain or a specific web address.
Wikipedia customisation for better readibility
It is not that hard to customize your favourite websites to improve and personalise your web experience, but you need to know a little of html and css. Not sure if there are tools for a wider audience.