600MB is definitely too much, especially if everything will be loaded all at once.
That. 
depends... if he makes a good 3d modeller in html and his assets are 600mb that is not bad...
website means anything... beginning with just a single card to a full fledged html game...
BINGO! I'm amazing game in mind. Working on story line. It would be really difficult for me to agree some game development company therefore, I'm considering option of developing something on own as pilot project.
But, I do not know what kind of developer I require as I don't have much knowledge with development.
What qualification and expertise would I require for filtering good modellor in HTML? What are other options apart from HTML?
Any pro's and con's on HTML you can throw light on?