There could be many different factors at play. To improve loading time and sharing of resources, Tableau Server renders many things client-side (on the browser) which may lead to small differences in how a viz looks in each browser. Essentially, it's like having three Spanish speakers translate the same sentence; they might all get the same meaning but individual word choices may differ. Tableau tries to offer the most consistent experience but something as simple as a new minor release (something Firefox would never-ever do ) will change how a viz renders.A good test is to add the url parameter ?:render=false which will make the server render the entire view. In theory, all browsers should now look the same when using that parameter. This can lead to more of a strain on the server if used in vast quantities but also works just fine for some users. I.e. http://tableauserver/views/sales/q1?:render=false
Here is some more info:
I hope this helps!
Thanks a lot, Diego, I was unfamiliar with that render parameter. Good to know.
Firefox has already updated to 37.0.2 and I don't see the issue anymore. Go figure.