Rated 5 out of 5 stars

1. Yes, it works well on USM and in Stylish, but I forgot to say that you have to try it with Tabs Always In Titlebar extension : https://addons.mozilla.org/en-us/firefox/addon/tabs-always-in-titlebar/.
2. Hide the app button is that this style should do. The purpose of this style is shrink the app button as much as possible and make it transparent. If you click on left border of the first tab the app button menu should appear. It also reduces tab width.
3. With "Tabs Always in Titlebar" installed, the "padding-left" property doesn´t appears to work well in USM, but yes with Stylish.
- Many thanks for your time.......
Great! but....
1. Do you now why this style doesn´t works ell with USM?
#main-window[tabsontop="true"][sizemode="normal"] #TabsToolbar {
padding-left: 2px !important;
I try the same code in Stylish and it works fine. I also try to use the "margin-left" property and it works well with USM and Stylsih, but at Firefox start, sometimes you have to wait a bit because USM takes some time on load. With "padding-left" in Stylish it doesn't happen.
2. Here is the complete code: http://tinypaste.com/725778d0.
If you can fix it, it would be appreciated.

This review is for a previous version of the add-on (0.9.1-signed). 

Hi, the code that you pasted here and also on the tinypaste, both work in both USM and Stylish, but there is something wrong with your styles, they are making the appmenu disappear. I don't exactly understand what you want to do with the styles.