title: CSS3 : 2 buttons in new line using flex concept
body: <p>I have a div . when I hover on it, I get 2 buttons side by side which i don't want. I have used the below code.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>.main_div{
    width:160px;
    height:160px;
    border:thin black solid;
    padding:5px;
    position:relative;
    
    /* Firefox */
    display:-moz-box;
    -moz-box-orient:horizontal;
    -moz-box-pack:center;
    -moz-box-align:center;
  
  /* Safari and Chrome */
    display:-webkit-box;
    -webkit-box-orient:horizontal;
    -webkit-box-pack:center;
    -webkit-box-align:center;
  
  /* W3C */
    display:box;
    box-orient:horizontal;
    box-pack:center;
    box-align:center;
  
    /* IE10 -Doesn't work yet! */
    display: -ms-flexbox;
    -ms-flex-align: center;
    -ms-flex-pack: center;
    -ms-box-orient:horizontal;
  
  }
  
  .main_div .hover_div{
    position: absolute;
    top: 0;
    right: 0;
    left: 0;
    bottom: 0;
    width:100%;
    height:100%;
    background: rgba(0,0,0,0.5);
    display: none;
    
  }
  
  .main_div .hover_div .upload_btn{
  background: white;
              padding: 3px 20px;
              color: #58666e;
              margin: 8px 0;
              
  }
  
  .main_div:hover .hover_div{
   /* Firefox */
    display:-moz-box;
    -moz-box-orient:horizontal;
    -moz-box-pack:center;
    -moz-box-align:center;
  
  /* Safari and Chrome */
    display:-webkit-box;
    -webkit-box-orient:horizontal;
    -webkit-box-pack:center;
    -webkit-box-align:center;
  
  /* W3C */
    display:box;
    box-orient:horizontal;
    box-pack:center;
    box-align:center;
  
    /* IE10 -Doesn't work yet! */
    display: -ms-flexbox;
    -ms-flex-align: center;
    -ms-flex-pack: center;
    -ms-box-orient:horizontal;
  
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="main_div"&gt;
    &lt;div class="hover_div"&gt;
    &lt;div class="upload_btn cursor_pointer"&gt;
                                        &lt;span&gt;xyz&lt;/span&gt;
                                      &lt;/div&gt;
                                      
                                      &lt;div class="upload_btn"&gt;
                                        &lt;span&gt;abc&lt;/span&gt;
                                      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>I want the upload_btn to be vertically center with having gap of 10-12px;</p>
  
  <p>Note : It should also work in IE10 to make the same design.</p>