Just as a bit of advice, look up (if you can) on the Builder's Accepted Applications part of the forum, this may help you see what you need to become a builder. Recently I became a builder and I had to build 5 projects that were roughly all 100 in height, and 60 blocks squared, so you've definately got to show some more and build some bigger stuff if you really want to become a builder.
And also, check out the WoM client avaliable here:
http://www.worldofminecraft.com/game_clientThe client poses alot of advantages over the browser version of MineCraft.
Chuck