vscode 本身已經支援 markdown 語法是文件預覽，但是預覽分割不好看，可以通過自己定義 vscode 的 markdown 顯示 css 風格來改變顯示效果。

1. vscode 選單 檔案->首選項->使用者設定
   在開啟的 settings.json 檔案中新增：

   {
       "markdown.styles": [ "file:///c:/my-md.css" ]
   }

2. 編輯 my-md.css 檔案內容如下：

   body{
       background: #000;
       font-family: Consolas, 新宋體, Georgia, Palatino, serif;
       color: #CCCCCC;
       line-height: 1;
       padding: 30px;
       margin:auto;
       /* max-width:42em; */
   }
   h1, h2, h3, h4, h5 {
       font-weight: 400;
       color: coral;
       /* border-bottom: 2px solid #999 !important; */
   }
   h1, h2, h3, h4, h5, p {
       margin-bottom: 24px;
       padding: 0;
   }
   h1 {
       font-size: 48px;
   }
   h2 {
       font-size: 36px;
       margin: 24px 0 6px;
   }
   h3 {
       font-size: 24px;
   }
   h4 {
       font-size: 21px;
   }
   h5 {
       font-size: 18px;
   }
   
   a {
       color: #61BFC1;
       margin: 0;
       padding: 0;
       text-decoration: none;
       vertical-align: baseline;
   }
   a:hover {
       text-decoration: underline;
   }
   a:visited {
       color: #466B6C;
   }
   ul, ol {
       padding: 0;
       margin: 0;
   }
   li {
       line-height: 24px;
   }
   li ul, li ul {
       margin-left: 24px;
   }
   p, ul, ol {
       font-size: 16px;
       line-height: 24px;
       /*max-width: 540px;*/
   }
   pre {
       padding: 0px 0px;
       /*max-width: 800px;*/
       white-space: pre-wrap;
       background-color: #666;
   }
   code {
       font-family: Consolas, Monaco, Andale Mono, monospace;
       line-height: 1.5;
       font-size: 13px;
   }
   aside {
       display: block;
       float: right;
       width: 390px;
   }
   blockquote {
       border-left:.5em solid #eee;
       padding: 0 2em;
       margin-left:0;
       /*max-width: 476px;*/
   }
   blockquote  cite {
       font-size:14px;
       line-height:20px;
       color:#bfbfbf;
   }
   blockquote cite:before {
       content: '\2014 \00A0';
   }
   
   blockquote p {  
       color: #666;
       /* max-width: 460px; */
   }
   hr {
       width: 540px;
       text-align: left;
       margin: 0 auto 0 0;
       color: #999;
   }
   
   /* Code added by cuiyu 2016-06-03 */
   table { 
       border-collapse: collapse; 
       border:1px solid #cad9ea; 
       empty-cells:show; 
       /* table-layout:fixed; */ 
       /* margin:0 auto; */ 
   } 
   
   td, th { 
       background-repeat:repeat-x; 
       height:30px; 
       border:1px solid #cad9ea; 
       padding: 0px 5px 0px 5px; 
   } 
   
   /* 首行縮排 */ 
   p {
       /* text-indent:2em; */
       white-space:pre-wrap;
   }
   
   
   /* Code below this line is copyright Twitter Inc. */
   
   button,
   input,
   select,
   textarea {
     font-size: 100%;
     margin: 0;
     vertical-align: baseline;
     *vertical-align: middle;
   }
   button, input {
     line-height: normal;
     *overflow: visible;
   }
   button::-moz-focus-inner, input::-moz-focus-inner {
     border: 0;
     padding: 0;
   }
   button,
   input[type="button"],
   input[type="reset"],
   input[type="submit"] {
     cursor: pointer;
     -webkit-appearance: button;
   }
   input[type=checkbox], input[type=radio] {
     cursor: pointer;
   }
   /* override default chrome & firefox settings */
   input:not([type="image"]), textarea {
     -webkit-box-sizing: content-box;
     -moz-box-sizing: content-box;
     box-sizing: content-box;
   }
   
   input[type="search"] {
     -webkit-appearance: textfield;
     -webkit-box-sizing: content-box;
     -moz-box-sizing: content-box;
     box-sizing: content-box;
   }
   input[type="search"]::-webkit-search-decoration {
     -webkit-appearance: none;
   }
   label,
   input,
   select,
   textarea {
     font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
     font-size: 13px;
     font-weight: normal;
     line-height: normal;
     margin-bottom: 18px;
   }
   input[type=checkbox], input[type=radio] {
     cursor: pointer;
     margin-bottom: 0;
   }
   input[type=text],
   input[type=password],
   textarea,
   select {
     display: inline-block;
     width: 210px;
     padding: 4px;
     font-size: 13px;
     font-weight: normal;
     line-height: 18px;
     height: 18px;
     color: #808080;
     border: 1px solid #ccc;
     -webkit-border-radius: 3px;
     -moz-border-radius: 3px;
     border-radius: 3px;
   }
   select, input[type=file] {
     height: 27px;
     line-height: 27px;
   }
   textarea {
     height: auto;
   }
   
   /* grey out placeholders */
   :-moz-placeholder {
     color: #bfbfbf;
   }
   ::-webkit-input-placeholder {
     color: #bfbfbf;
   }
   
   input[type=text],
   input[type=password],
   select,
   textarea {
     -webkit-transition: border linear 0.2s, box-shadow linear 0.2s;
     -moz-transition: border linear 0.2s, box-shadow linear 0.2s;
     transition: border linear 0.2s, box-shadow linear 0.2s;
     -webkit-box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1);
     -moz-box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1);
     box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1);
   }
   input[type=text]:focus, input[type=password]:focus, textarea:focus {
     outline: none;
     border-color: rgba(82, 168, 236, 0.8);
     -webkit-box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1), 0 0 8px rgba(82, 168, 236, 0.6);
     -moz-box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1), 0 0 8px rgba(82, 168, 236, 0.6);
     box-shadow: inset 0 1px 3px rgba(0, 0, 0, 0.1), 0 0 8px rgba(82, 168, 236, 0.6);
   }
   
   /* buttons */
   button {
     display: inline-block;
     padding: 4px 14px;
     font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
     font-size: 13px;
     line-height: 18px;
     -webkit-border-radius: 4px;
     -moz-border-radius: 4px;
     border-radius: 4px;
     -webkit-box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
     -moz-box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
     box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.2), 0 1px 2px rgba(0, 0, 0, 0.05);
     background-color: #0064cd;
     background-repeat: repeat-x;
     background-image: -khtml-gradient(linear, left top, left bottom, from(#049cdb), to(#0064cd));
     background-image: -moz-linear-gradient(top, #049cdb, #0064cd);
     background-image: -ms-linear-gradient(top, #049cdb, #0064cd);
     background-image: -webkit-gradient(linear, left top, left bottom, color-stop(0%, #049cdb), color-stop(100%, #0064cd));
     background-image: -webkit-linear-gradient(top, #049cdb, #0064cd);
     background-image: -o-linear-gradient(top, #049cdb, #0064cd);
     background-image: linear-gradient(top, #049cdb, #0064cd);
     color: #fff;
     text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.25);
     border: 1px solid #004b9a;
     border-bottom-color: #003f81;
     -webkit-transition: 0.1s linear all;
     -moz-transition: 0.1s linear all;
     transition: 0.1s linear all;
     border-color: #0064cd #0064cd #003f81;
     border-color: rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.25);
   }
   button:hover {
     color: #fff;
     background-position: 0 -15px;
     text-decoration: none;
   }
   button:active {
     -webkit-box-shadow: inset 0 3px 7px rgba(0, 0, 0, 0.15), 0 1px 2px rgba(0, 0, 0, 0.05);
     -moz-box-shadow: inset 0 3px 7px rgba(0, 0, 0, 0.15), 0 1px 2px rgba(0, 0, 0, 0.05);
     box-shadow: inset 0 3px 7px rgba(0, 0, 0, 0.15), 0 1px 2px rgba(0, 0, 0, 0.05);
   }
   button::-moz-focus-inner {
     padding: 0;
     border: 0;
   }