Update (March 2, 2022): As a group of developers who met through the Opera Browser community, we originally started this project with plans to patch malformed web pages that were improperly rendered when using Opera Presto. Before this project was completed, Opera migrated its rendering engine to Chromium, eliminating most of these rendering issues.
With the release of Fix the Web, you now can start applying CSS patches to websites easily. Continue reading to learn how easy it is to do it. Read more on the blog.
Tip: before sending a pull request after you add your patch to the patches.json file, validate the entire JSON file in Opera Browser at JSONLint.
Install the lastest stable version in the Opera addons catalog