What's the general approach on modifying 3rd party websites for testing? For example, I want to modify certain aspects of a random website (HTML, js, css, images whatever) that I do not control and see locally modified site with my changes.
There are multiple ways:
1. copy everything to local server and do whatever I want.
This is a bit tedious, messy and won't replicate exact behavior of original server: some headers might not be the same (CORS for example). Also, host name is different (but this can be "fixed" by overriding host name in
browserify), and sometimes images as well (as sprites). If you don't have the source files, you can still resort to the methods below.
If you want to modify the CSS and have it persist, you can use a Chrome extension like Live CSS editor.
A proxy to do regex replacements is another valid approach - see Proxomitron for Windows, which also has plugins that can intercept SSL traffic.