add error css

IPython/html/static/base/less/error.less

@@ -0,0 +1,20 b''
+div.error {
+  margin: 2em;
+  text-align: center;
+}
+
+div.error > h1 {
+    font-size: 500%;
+    line-height: normal;
+}
+
+div.error > p {
+    font-size: 200%;
+    line-height: normal;
+}
+
+div.traceback-wrapper {
+    text-align: left;
+    max-width: 800px;
+    margin: auto;
+}

IPython/html/static/base/less/style.less

@@ -1,4 +1,4 b''
 @import "variables.less";
 @import "mixins.less";
 @import "flexbox.less";
-
+@import "error.less";

IPython/html/static/style/ipython.min.css

@@ -18,6 +18,10 b''
 .start{-webkit-box-pack:start;-moz-box-pack:start;box-pack:start;}
 .end{-webkit-box-pack:end;-moz-box-pack:end;box-pack:end;}
 .center{-webkit-box-pack:center;-moz-box-pack:center;box-pack:center;}
+div.error{margin:2em;text-align:center;}
+div.error>h1{font-size:500%;line-height:normal;}
+div.error>p{font-size:200%;line-height:normal;}
+div.traceback-wrapper{text-align:left;max-width:800px;margin:auto;}
 .center-nav{display:inline-block;margin-bottom:-4px;}
 .alternate_upload{background-color:none;display:inline;}
 .alternate_upload.form{padding:0;margin:0;}

IPython/html/static/style/style.min.css

@@ -1385,6 +1385,10 b' ul.icons-ul{list-style-type:none;text-indent:-0.7142857142857143em;margin-left:2'
 .start{-webkit-box-pack:start;-moz-box-pack:start;box-pack:start;}
 .end{-webkit-box-pack:end;-moz-box-pack:end;box-pack:end;}
 .center{-webkit-box-pack:center;-moz-box-pack:center;box-pack:center;}
+div.error{margin:2em;text-align:center;}
+div.error>h1{font-size:500%;line-height:normal;}
+div.error>p{font-size:200%;line-height:normal;}
+div.traceback-wrapper{text-align:left;max-width:800px;margin:auto;}
 body{background-color:white;position:absolute;left:0px;right:0px;top:0px;bottom:0px;overflow:visible;}
 div#header{display:none;}
 #ipython_notebook{padding-left:16px;}