Panning on a map within a web page

[grm3]

There's a website I use to check traffic conditions for my commute (511nj.org), and it has a map that shows traffic congestion by colors (511nj.org :: Traffic Map). On my desktop PC, I can hold my mouse button and drag the map to pan up/down & left/right to see different sections of the state. On my phone (Samsung Fascinate stock ED01), I cannot get the map to do this. I can only move the entire page, not the map image. Is it possible to do this with the mobile browser? I've tried the stock browser and Dolphin HD with no luck.