I have created a left side bar. Is it possiable to make the side bar fixed on the screen. Whenever i make the screen smaller, the left side bar disappears. 

```
<div class="col-sm-3 col-md-2 sidebar">
          <ul class="nav nav-sidebar">
            <li class="active"><a href="index.php">Categories <span class="sr-only">(current)</span></a></li>

```

This is my code for the side bar. it gets the categories name using php from mySql.