Highlighting search terms in content is a great way of displaying the relevancy of the page to its viewers. In Wordpress, this can be achieved with the help of a simple tweak. Both title and post contents can be highlighted using the following code snippet.

In the WordPress theme’s function.php file, paste the following code:

function hls_set_query() {
  $query  = attribute_escape(get_search_query());
  if(strlen($query) > 0){
    echo '
      <script type="text/javascript">
        var hls_query  = "'.$query.'";
      </script>
    ';
  }
}
function hls_init_jquery() {
  wp_enqueue_script('jquery');
}
add_action('init', 'hls_init_jquery');
add_action('wp_print_scripts', 'hls_set_query');

Open the theme’s header.php and paste the following code (just before the </head> tag):

<style type="text/css" media="screen">
  .hls { background: #D3E18A; } /* <- Change the CSS style of */
                                /*    highlighted texts here. */
</style>
<script type="text/javascript">
jQuery.fn.extend({
  highlight: function(search, insensitive, hls_class){
    var regex = new RegExp("(<[^>]*>)|(\\b"  search.replace(/([-.* ?^${}()|[\]\/\\])/g,"\\$1")  ")", insensitive ? "ig" : "g");
    return this.html(this.html().replace(regex, function(a, b, c){
      return (a.charAt(0) == "<") ? a : "<strong class=\""  hsl_class  "\">"   c   "</strong>";
    }));
  }
});
jQuery(document).ready(function($){
  if(typeof(hls_query) != 'undefined'){
    $("#post-area").highlight(hls_query, 1, "hls"); // <- Change 'post-area' to ID of HTML tag you
                                                    //    want to highlight search terms in.
  }
});
</script>