Is it to possible add placeholder text for link fields?
You could do something like this in

function formalter(){
$form['#after_build'][] = 'mytheme_after_build'; 
}
function mytheme_after_build(&amp;$form, &amp;$form_state){
    $form['field_twitter_link']['und'][0]['url']['#attributes']['placeholder']=t('my new');
    return $form;
}


Taken from here https://drupal.org/node/1002560