As you know, Firefox's appearance changed significantly at version 4, version 29, and version 57. What appearance are you looking for?

Many UI changes are possible by applying custom style rules using a file called userChrome.css. However, some changes made by, for example, Classic Theme Restorer, are not possible in Firefox 57 because they involved restoring missing structural parts of the browser. Style rules can't do that.

Speaking of CTR, its author posted a huge trove of custom style rules. There also are forums dedicated to this topic. Let me give you a few links and if you have specific follow-up questions, please let us know. And let us see what you end up with.

• CTR rules: https://github.com/Aris-t2/CustomCSSforFx
• Where to Find Style Recipes
• How to Create a userChrome.css File

Seems as if everyone who offers help assumes that all who seek it are pretty much computer literate - employ terms that don't help any for people who just want a simple un-skilled answer for how to do something or find something on a computer. Microsoft 10 didn't help a bit by requiring a number of choices to be selected - and number of places it puts things - that a simple high school or college graduate of few years ago cannot figure out or memorize because the terms assume you half way know the answer before asking a question

ajn2 said

Seems as if everyone who offers help assumes that all who seek it are pretty much computer literate - employ terms that don't help any for people who just want a simple un-skilled answer for how to do something or find something on a computer. Microsoft 10 didn't help a bit by requiring a number of choices to be selected - and number of places it puts things - that a simple high school or college graduate of few years ago cannot figure out or memorize because the terms assume you half way know the answer before asking a question

I don't see a question in your diatribe. If your intention is to post disruptive comments and don't actually want help, please go elsewhere.

If you do want help please ask a question in a new thread and please provide the requested information so that we can try to help you. https://support.mozilla.org/en-US/questions/new/desktop

Hi ajn2, the phrase "computer literate" is pretty general, and there is a really huge range of users. Some people struggle with distinguish between a computer desktop and a web browser home page. The fact that you want to change how your software looks and are willing to search out ways to do it indicates to me that you are above the basic level. Go ahead and start a new question and get into detail about what you want to change. The worst thing that can happen is we won't be able to help you. But you might get everything you want.