The responsive.css file contains 3 non functional rules which try to change the placeholder text.

You can't change the text content of a placeholder with CSS, also if these rules did work they would be changing the search phrase from whatever language the user is using to English which would confuse users.

Responsive.css:

    .action-bar .search-box .inputbox ::-moz-placeholder {

        content: "Search...";

      }

**

      .action-bar .search-box .inputbox :-ms-input-placeholder {

          content: "Search...";

      }

**

      .action-bar .search-box .inputbox ::-webkit-input-placeholder {

          content: "Search...";

      }

Suggestion:

Those rules were added sometime between phpBB 3.1.7 and 3.2.0

If placeholder text being cut off in the action bar search boxes is a concern, ellipsis can be added using placeholder-shown, see example below.

.action-bar .search-box input.inputbox:placeholder-shown {

text-overflow: ellipsis;

}