When the window is not wide enough, or when the job name is too long, the "Cancel" button in the Job view of the web UI is not visible because it is the first element that gets wrapped down and gets covered by the secondary navbar (the tabs). This causes us to often need to resize the browser wider than our monitor in order to use the cancel button.
In general, the use of Bootstrap's ".navbar-fixed-top" is problematic if the content may wrap, especially if the content's horizontal width if not known & fixed. The ".navbar-fixed-top" uses fixed positioning, and therefore any unexpected change in height will result in overlap with the rest of the normal-flow content in the page. The Bootstrap docs explain this in their "Overflowing content" callout.
I am submitting a PR which does not attempt to resolve all issues with the fixed navbar approach, but attempts to improve the situation by using less horizontal space and by altering the layout approach of the Cancel button.