[Docs] Add introduction to alexnet loading pad

Author: CharlesLiuyx

css/playground.css

@@ -65,6 +65,7 @@ main {
     width: 100%;
     height: 100%;
     /*position: relative;*/
+    text-align: center;
     border: 0!important;
     z-index: 2;
 }
@@ -76,6 +77,19 @@ main {
     width: 350px;
 }
 
+.loading-label {
+
+    font-size: 28px;
+    line-height: 32px;
+    position: absolute;
+    margin-top: 100px;
+    width: 100%;
+    text-align: center;
+    color: #FFFFFF;
+
+}
+
+
 #controlPanel {
 
     background-color: #02242F;
@@ -152,4 +166,10 @@ main {
 
 #nav-collapse {
     z-index: 100!important;
+}
+
+.span-estimate {
+
+    font-size:20px;
+
 }

html/playground/alexnet.html

@@ -114,6 +114,9 @@
 
     <div id="loadingPad">
         <img id="loading" src="../../assets/img/loading/mouseLoading.gif">
+        <div class="loading-label">
+            Downloading AlexNet pre-trained model...<br>236MB <span class="span-estimate">- Estimate 20s to 5min</span>
+        </div>
     </div>
     <div id="modelArea"></div>
     <div id="controlPanel">

html/playground/alexnet_zh.html

@@ -114,6 +114,9 @@
 
     <div id="loadingPad">
         <img id="loading" src="../../assets/img/loading/mouseLoading.gif">
+        <div class="loading-label">
+            正在下载AlexNet预训练模型...<br>236MB <span class="span-estimate">- 估计20s-5min</span>
+        </div>
     </div>
     <div id="modelArea"></div>
     <div id="controlPanel">