I want to disallow users from searching without a query string (at least one character). To achieve this, I tried to disable the search submit button when the search box is empty, and restoring the enabled state when the user inputs something.
The problem is that the search engine appears to be disabled. Then I put a label inside the search box (placeholder), but since the colors of text are grey, it still has a "disabled look".
Without using labels, which option should I follow? I already think on some alert box to alert the user, but it seems to be too intrusive.
Related: Search box must contain at least three letters - how to convey? but it uses labels.