Placeholder by itself will not disappear when you click the text field. I guess you need a bit of Javascript to achieve that.
<input type="text" onfocus="if(this.value=='<?php _e( 'Search here..' ); ?>'){this.value="";}" onblur="if(this.value==''){this.value="<?php _e( "Search here..' ); ?>';}" value="<?php _e( 'Search here..' ); ?>">