Yosemite: Safari's window is too wide

Solution 1:

You can enable "Develop" menu in Preferences > Advanced.

Then you can select choose the User Agent to be iPhone or whatever. enter image description here

And then resize the window appropriately:

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Edit: This doesn't get around the minimum width for the window. Here is a workaround. Go to View > Show Sidebar. This pulls out the sidebar, which can be resized making the viewport smaller.

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