I'm building a site right now and am wondering how to edit my php code for my site search so that it doesn't allow any JS or HTML for security purposes. I have the code listed below and was wondering how you would go about coding this. Also feel free to include any pointers or tips....Thank you.

<form action="<?php echo home_url(); ?>/" method="get" id="searchform">
<fieldset>
<div id="searchbox">
<input class="input" name="s" type="text" id="keywords" value="<?php _e('to search, type and hit enter','cosmotheme') ?>" onfocus="if (this.value == '<?php _e('to search, type and hit enter','cosmotheme') ?>') {this.value = '';}" onblur="if (this.value == '') {this.value = '<?php _e('to search, type and hit enter','cosmotheme') ?>';}">
</div>
<p class="button hover square">
<input type="submit" name="search" value="<?php _e('Search','cosmotheme') ?>">
</p>
</fieldset>
</form>