Checking the source on github, you'll find in syntax.php that the text box has the id
qsearch2__in. The following CSS will widen the box and make the background color yellow. In Firefox, unfortunately, it will widen all text boxes. In IE only the query box of the given id.
#qsearch2__in, input[type=text] {
width: 300px;
background-color: yellow;
}
Also, since I see that the box has a class named edit, this will work in Firefox:
input.edit[type=text] {
. . . .
}
Like the previous, of course, it will affect any text input with the class named
edit.
You could also alter the code in syntax.php and add a width attribute to the query box, and that will give you what you want:
$renderer->doc .= '<input type="text" id="qsearch2__in" width="60" accesskey="f" name="id" class="edit" autocomplete="off">'."\n";