one quick and dirty solution to get rid of that searchform error is to give no label to the assistive-text.
so remove the line: <label class=”assistive-text” for=”s”><?php _e( ‘Search’, ‘cleanretina’ ); ?></label>
Search will work without it and html Validation is than correct.
i now did it this way: i removed the class s and set an id s
<form action="<?php echo esc_url( home_url( '/' ) ); ?>" class="searchform clearfix" method="get"> <label class="assistive-text" for="s"><?php _e( 'Search', 'cleanretina' ); ?></label> <input id="s" class="field" name="s" type="text" placeholder="<?php esc_attr_e( 'Search', 'cleanretina' ); ?>"> </form><!-- .searchform -->
and this will do the trick
btw you can stay class s but add id s
<form action="<?php echo esc_url( home_url( '/' ) ); ?>" class="searchform clearfix" method="get"> <label class="assistive-text" for="s"><?php _e( 'Search', 'cleanretina' ); ?></label> <input id="s" class="s field" name="s" type="text" placeholder="<?php esc_attr_e( 'Search', 'cleanretina' ); ?>"> </form><!-- .searchform -->