Viewing reputation changes on Stack Overflow produces a nice graph which can be 'zoomed in' on to view more detailed reputation changes, for example. Is this using a library or is it custom written? If it's a library, which is it?
Looks like highcharts because inspecting the DOM reveals stuff such as:
<svg ...> <defs> <clipPath id="highcharts-1"> ... <g class="highcharts-grid" zIndex="1"> ...
There are actually 2 reputation graphs,
I think the one you are referring is the the graph in reputation tab. The graph in reputation tab is rendered using highcharts in fact it is a master-detail type of chart.
While coming to the other one in the summary tab, its a html graph not a highcharts one.