The following is for base install theme P2 v1.5.4 on WP 3.9.1.
In style.css, the #wrapper style rule starts at line 121 and includes the following on line 126:
If change width to <= 958px and log on, the admin <div id="postbox">"Hi, admin. Whatcha up to?"</div> section is no longer functional as it simply displays the textarea, nothing else. This occurs on IE11 and some earlier versions of IE, but not on other Web browsers including FF30, CH35. Any idea what is causing this? Would like to have the width a bit less than 958px.