php - First option in dropdown disables submit button on form -

i have form on site hooked mailchimp. seems work apart if top option (currently 'all') selected dropdown menu.

here code form:

    <?php if(is_front_page()) { ?>  <style> .fixed_header.social_header #main{padding-top: 0px!important;} .mailchimp{ width: 100%;background: url(<?php bloginfo('template_url') ?>/images/bg_mc.png) no-repeat; background-position: left top; background-size: 100% 100% ; min-height: 399px; padding: 154px 0 20px 0;} .inner-mailchimp{margin: 0 auto; width: 805px; text-align: center;} .mailchimp h1, .mailchimp h3{color: #fff;}  /*#news_mc, #everything, #business_mc, #technology_mc, #dnd_mc, #smedia_mc{display: none;}*/ #mc_embed_signup{background: none!important;} #everything_mc{ display: block;} .form_mc{width: 400px; float: left;} #mc_embed_signup .mc-field-group select{ padding: 7px 0!important;} #dnd_mc, #news_mc, #business_mc, #technology_mc, #smedia_mc{display:none;} .mc-field-group label{color: #fff;} #mc-embedded-subscribe-form .clear{visibility: visible; overflow: visible; right: -271px;  top: -13px; background: url(<?php bloginfo('template_url');?>/images/c.png ); position: relative;} #mc_embed_signup .button{ background-color: #005cbf!important; font-weight: normal!important;}  </style> <script>  function fill_email(my_mail){     var fillupemail = document.getelementbyid(my_mail).value;     //alert(fillupemail);     document.getelementbyid('unique_news').value = fillupemail;     document.getelementbyid('unique_business').value = fillupemail;     document.getelementbyid('unique_dnd').value = fillupemail;     document.getelementbyid('unique_everything').value = fillupemail;     document.getelementbyid('unique_smedia').value = fillupemail;     document.getelementbyid('unique_technology').value = fillupemail;  }  function mailchange(id){     var x = document.getelementbyid(id);      if(x.value == 'everything'){         document.getelementbyid('dnd_mc').style.display='none';         document.getelementbyid('news_mc').style.display='none';         document.getelementbyid('business_mc').style.display='none';         document.getelementbyid('technology_mc').style.display='none';         document.getelementbyid('smedia_mc').style.display='none';          document.getelementbyid(x.value+'_mc').style.display='block';     }     if(x.value == 'news'){         document.getelementbyid('everything_mc').style.display='none';         document.getelementbyid('dnd_mc').style.display='none';         document.getelementbyid('business_mc').style.display='none';         document.getelementbyid('technology_mc').style.display='none';         document.getelementbyid('smedia_mc').style.display='none';          document.getelementbyid(x.value+'_mc').style.display='block';     }     if(x.value == 'business'){         document.getelementbyid('everything_mc').style.display='none';         document.getelementbyid('dnd_mc').style.display='none';         document.getelementbyid('news_mc').style.display='none';         document.getelementbyid('technology_mc').style.display='none';         document.getelementbyid('smedia_mc').style.display='none';          document.getelementbyid(x.value+'_mc').style.display='block';     }     if(x.value == 'technology'){         document.getelementbyid('everything_mc').style.display='none';         document.getelementbyid('dnd_mc').style.display='none';         document.getelementbyid('news_mc').style.display='none';         document.getelementbyid('business_mc').style.display='none';         document.getelementbyid('smedia_mc').style.display='none';          document.getelementbyid(x.value+'_mc').style.display='block';     }     if(x.value == 'dnd'){         document.getelementbyid('everything_mc').style.display='none';         document.getelementbyid('news_mc').style.display='none';         document.getelementbyid('business_mc').style.display='none';         document.getelementbyid('technology_mc').style.display='none';         document.getelementbyid('smedia_mc').style.display='none';          document.getelementbyid(x.value+'_mc').style.display='block';     }     if(x.value == 'smedia'){         document.getelementbyid('everything_mc').style.display='none';         document.getelementbyid('dnd_mc').style.display='none';         document.getelementbyid('news_mc').style.display='none';         document.getelementbyid('business_mc').style.display='none';         document.getelementbyid('technology_mc').style.display='none';          document.getelementbyid(x.value+'_mc').style.display='block';     }  } </script>  <div class="mailchimp">     <div class="inner-mailchimp">         <h1>scientia potentia est</h1>         <h3>knowledge power</h3>         <div class="form_mc">             <?php include('mailchimp-everything.php'); ?>             <?php include('mailchimp-news.php'); ?>             <?php include('mailchimp-business.php'); ?>             <?php include('mailchimp-technology.php'); ?>             <?php include('mailchimp-dnd.php'); ?>             <?php include('mailchimp-smedia.php'); ?>         </div><!-- form -->         <div class="form_mc">              <div class="everything_mc display_mc" id="mc_embed_signup"><form>             <div class="mc-field-group selectmail_mc">                 <label for="mce-email">interest </label>                 <select onchange="mailchange(this.id)" id="selectmail_c">                     <option value="everything">all</option>                     <option value="news">news</option>                     <option value="business">business</option>                     <option value="technology">technology</option>                     <option value="dnd">design & development</option>                     <option value="smedia">social media</option>                 </select>             </div></form>             </div>          </div><!-- form -->         <small style="color: #ffffff; float: left; font-size: 13px; margin-bottom: 20px; text-align: center; width: 100%;">don't worry there's no spam intriguing posts , <u>free</u> resources.</small>     </div> </div>  <?php } ?> 

i have checked through separate files each selection on drop-down seem correct believe problem must in code. unfortunely can't understand enough decipher problem be.

edit: this site , form below header.

any appreciates, thanks!

could if select different option drop down , go first dropdown option works? (unfortunatly cannot post comments due low rep) have feeling issue may mailchange function not called on page load have 'select' option instead of defaulting it.