Maybe an issue of the Firefox beta? It works perfectly in Firefox 54 on Windows.

so in the css-class:

.siteSelector a.title > span {
    max-width: 161px;
    display: inline-block;
    overflow: hidden;
    text-overflow: ellipsis;
}

display: inline-block; makes the difference. Omitting it will show the site name partially again. I don't know if Firefox does it differently in v55 or It is just a Piwik problem.

Hi,
I can reproduce this in Firefox Developer Edition (55.0b6) on Linux.
It works correctly in Chromium and Firefox ESR.

But in Firefox 55 only the ellipsis is printed.

Oddly disabling the following CSS lines doesn't change anything.

overflow: hidden;
text-overflow: ellipsis;

If I change the max-width: to below 155px it also works again. (Changing the width of the surrounding <a> doesn't fix it, but decreasing the font size does.

I think this is a bug in Firefox as this can't be intended.

I created a minimal example where the error occurs: https://jsfiddle.net/dn993xcL/3/
(unfortunately the css structure is lost in it)

@Findus23 You want to submit to Firefox Bugzilla?
---Edited:
Upstream Bug:
https://bugzilla.mozilla.org/show_bug.cgi?id=1378127

Done: https://bugzilla.mozilla.org/show_bug.cgi?id=1378131

(I hope it is understandable as it's my first bug report at Mozilla)

To sum it up:

Firefox is behaving as it should and we need to remove the display: inline-block; from the inner span. (which is what @pouyana initially suggested)

Let's see what the UI test says: https://travis-ci.org/piwik/piwik/builds/250107854