I am having some issues with this DIV not getting centered.
I am sure it is something with CSS,

I need some corrections to CSS below and to get rid of unnecessary CSS statements if not needed

I would like the div to be centered and 75% wide

Thanks,

```
  .css_main_popup {
    transition: opacity 10ms;
    visibility: hidden;
    position: absolute;
    top: 10px;
    right: 10px;
    font-size: 30px;
    font-weight: bold;
    text-decoration: none;
    color: #333;
    margin: auto;
    margin-left: auto;
    margin-right: auto;
    padding: 10px;
    background: #fff;
    border-radius: 5px;
    width: 95%;
    height: 90%;
    overflow: auto;
    align-self: center;
  }

```

HTML

```
<!DOCTYPE html>
<html lang="en">

    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>SMT Explorer</title>
        <link rel="stylesheet" href="explorer.css">
        <link rel="stylesheet" href="main.css">
    </head>

    <body>
        <div id="main_div" style="position: relative; "></div>

        <div id="popup_factory" class="css_main_popup">
            <a class="css_close_popup" href="#" style='text-align:right' onclick="CloseFPopup()">&times;</a>
        </div>

        <div id="popup_stations" class="css_main_popup">
            <a class="css_close_popup" href="#" style='text-align:right' onclick="CloseSPopup()">&times;</a>
        </div>

        <script type="text/javascript" src="explorer.js"></script>
    </body>

</html>

```

[![enter image description here](https://i.stack.imgur.com/fB5QF.png)](https://i.stack.imgur.com/fB5QF.png)