
to reproduce, either access jquery.org with a mobile device, or use a desktop browser and reduce the browser screen width. Very quickly the search input field becomes so narrow that it is unusable. However, there is room to have it wider...
the width is set to 20% :
nav#main .searchform {
width: 20%;
}
however, when the search input field is on a small screen and comes on its own line, it could afford a wider width than that...