execCommand('createLink') doesn't work in Firefox

I highlight the text and click on the <div class="link"></div>, typing link url into the textfield and press enter, but link doesn't creating in firefox ( in Chrome / Safari it works fine ).

create events:

    events:{
        'click .link':              'toggleLink',
        'keypress [name="link"]':   'setUrl'
    },

functions:

toggleLink: function(e){
        if(this.options.nodes.url){
            this.$el.find('[name="link"]').val(this.options.nodes.url);
        }

        this.lastRange = window.getSelection().getRangeAt(0);
        this.$el.find('[name="link"]').focus();
    },

setUrl: function(e){
        if(e.which == 13){
            e.preventDefault();
            this.$el.find('[name="link"]').blur();
            window.getSelection().addRange(this.lastRange);
            var url = $(e.currentTarget).val();
            if(url.length > 0){
                document.execCommand('createLink', false, url);
            }else{
                document.execCommand('unlink', false, null);
            }               
        }
    }

What i'm doing wrong and why firefox don't want to create link? thx!