Hi,
It depends on the container width and position as well, so if the layer item width gets small, it affects the search bar as well.
Maybe using a media query custom CSS, something like this:
[html]@media screen and (max-width: 523px) {
.asp_main_container {
width: 340px !important;
min-width: 340px !important;
margin-left: -120px !important;
}
}[/html]
So this basically changes the bar to 340 pixels width on screens lower than 524 pixels, and kind of positions it to the middle with a negative margin due to the small inner layer. This should be close to a possible solution.