It could be a couple differnt things. First of all, you can leave your browser window open, save any changes you make in VS, then hit the refresh button in your browser.
Second, I normally use the "View in Browser" function....Either "Control + Alt + W" or select it from the File menu.
If none of these work, try clearing your browser cache. You may be caching your previous work and it is loading it instead of your new work.
Good luck
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