Have you been trying use websites, like Transport for London (TfL) journey planner, in Firefox recently (or for a while) and found that they seem broken - e.g. TfL only shows the bus route?! Well you're not the only one. Since Firefox version 42 Mozilla has enabled Tracking Protection which is generally a very good thing (as there's way too many trackers out there keeping tabs on where/when/what you're up to). Sadly some sites aren't designed to cope with that so they fail to work properly - like TfL and others.
Fortunately it's easy to fix once you know how: When Firefox blocks tracking elements it helpfully puts an additional 'shield'
icon in the URL bar to indicate the fact. If you click on the shield icon it shows a button to 'Disable protection for this site' - which disables tracker blocking for that site - you'll then see a line drawn through the shield to indicate this.
One other thing is that if you also use other blocker plugins/extensions in Firefox (e.g. uBlock, Ghostery, AdBlockPlus) you may also need exempt the site in those too.