Microsoft leveraged their dominance of desktop computing to gain dominance of browser installed base with IE. Having won the battle, they stopped improving the browser as an application platform.
During the first period, Microsoft developed and deployed a variety of browser technologies such as Dynamic HTML (aka the DOM) and XMLHTTPRequest that moved the browser toward being a viable application platform. During the second period, IE stagnated and it was left to Firefox and, later, Chrome to pick up the baton. But they had to fight for market share for several years before having enough influence to make significant progress. IE has recently caught up, but that still leaves several years before enterprise customers will deploy the improvements.
Thus in 2014 there are still major gaps in the browser platform that really should have been solved some years back, and a large portion of installed base still using the transitional IE 8 and 9.