WojciechMigda: As for the Fullscreen operation, then at least for Firefox running on Linux you can use the F11 key or the menu option Main->View->Fullscreen Mode.
I use the same F11 key in Chrome on Windows, but as mentioned, this only works for a short time after you launch the game pop-up window. If I forget to switch to full-screen then, and launch a round, it's too late to switch to full screen then, and I can only maximize the window.
TWO evidently went a different path: they assigned a dedicated keyboard shortcut to the Full Screen mode, namely F2. You can press F2 as many times in TWO as you want, and the switch to Full Screen always works. Perhaps if WGT assign a dedicated keyboard shortcut to full-screen as well, instead of relying on the browser's default keyboard shortcut (F11), this would function more reliably here.
As to wide-screen support on TWO, TWO offers it, but it does not work reliably. On smaller resolutions, the outer edge of the picture is cut off (say, a tiny bit of the left-most letter in the chat window), while on higher resolutions, quite a chunk of the picture and the overhead mini-map is missing. Perhaps this is also related to the computer's graphics card; don't know. On WGT.com, we have no wide-screen support as yet, but at least the full picture is always shown in full-screen mode.