I have had a brief look at the p&l calculator and I don't get it. Perhaps you could provided a demo on what it would be used for.
Ok, here's an example for pnl page:
1. Enter a ticker and request quotes (either by hitting enter or clicking the button) -> the form will become disabled while loading. If provider answers that it doesn't know such a ticker, the input field will become red. If everything's fine, other parts of the page will be revealed: "Underlying chart" (orange) and "Risk profile" (green).
2. Use the plus button to add legs to your strategy. Apply your desired what-if scenarios. Every parameter can be changed at any time and the chart below will reflect the changes instantly.
3. Look at the chart and repeat step 2 until you satisfied with the builded strategy. Go to your trading terminal and execute it (be aware that yahoo and google both provide delayed quotes, so the actual prices may be a little different).
4. For your convenience, pnl calculation can be tweaked by this form. Yuo can alter both price span and calculation step (in dollars).
P.S. I've detected many problems on the step 1 of this demo (people just get stuck here because nothing happens for a long time after clicking the button). It takes time to request quotes from the provider, but for me it rarely exceeds 1-2 seconds. I'll try to figure out what happens and fix it, at least I'll create a more obvious "loading..." label than just disabling the "request" button. Stay tuned, guys, I'm working on it.
P.P.S. I always test my app in google chrome and sometimes in mozilla firefox, so it would be better if you use the same browser (another one should also work though).