Call to undefined function base_url()

[eluser]Anandafit[/eluser]
Hi,
I am new for the this framework. I am fallowing a tutorial and now I have a error called "Call to undefined function base_url()"

I used this function in my view as fallow,
"<link href=”<?= base_url();?>css/default.css” rel=”stylesheet” type=”text/css” />"

I configured autoload.php file for url helper as fallow,
"$autoload['helpe'] = array('url','form','text','date','security');"

But I didn't any change for "$config['base_url']= "http://your-site.com/";" in config.php.

I think that this error appear as a result of "$config['base_url']" in config.php. But I don't know really is it.

Help me to solve this.

Regards,
Ananda,