Text showing over image submit button on Search form

This is my first Perch project and I am not a php developer but have still managed to work out how to use Perch for my latest project and really love working with it.

I have a small but irritating problem, which I hope somebody may be able to help me with.

I have a popup box for my search page with an icon submit button. I build this working from the sample Perch 'search' template and it works beautifully... But I just can't work out how to remove the 'Submit Query' text from showing over the submit icon. I have looked for it in my style sheets and is but it has completely eluded me. See image below:

I thought it would just be a matter of removing the text from the value="" but as you can see from the code below I am using, there is already no text and it is still there.

            <!-- Search --> 
                        <div class="search-include">
                            <div class="search-button">
                                <a href="#"><i class="icon-search"></i></a>
                            </div>
                            <div class="popup-search">
                                <perch:form id="search" method="get" action="/search.php" role="search" >
                                    <perch:input type="search" value="Search." onblur="if(this.value=='') this.value='Search.';" onfocus="if(this.value=='Search.') this.value='';" class="ft" id="q" />
                                    <perch:input type="submit" value="" class="fs" />
                                </perch:form>
                            </div>  
                        </div>
                        <!-- /Search -->

I am at the very end of the project and with the help of the 'documents' I have managed to figured out more complicated problem but at the moment this one has beaten me.