Microsoft yesterday announced redesigned F12 developer tools UI in IE11. With IE11, Microsoft came up with a vertical lineup of icons which caused great confusion among web developers. This update addresses concerns that many users had with the vertical navigation model and now they are back with a more traditional horizontal model.
When we introduced the vertical navigation model, our goal was to optimize for vertical real estate. Your feedback validated that we successfully achieved that goal. However, it also became clear that using a vertical navigation model with icons identifying complex tools, lead to hesitation and confusion for novice and expert users alike.
In order to address those issues, we implemented a more traditional navigation interface that sits horizontally at the top of the tools. As part of this change, the tool icons were removed and replaced with the tool’s name. We retained the tool notification badges—like the debugger pause icon or the console error count—and removed tool names from their respective toolbars to make more space available to the tools themselves.
Source: IE Blog