That's something CSS alone can't do, because there are no tags to differentiate the input field from the input button, and they are not exactly adjacent.
You would need to add a class tag in /includes/templates/your_template/sideboxes/tpl_search_header.php.
PHP Code:
if (strtolower(IMAGE_USE_CSS_BUTTONS) == 'yes') {
$content .= zen_draw_input_field('keyword', '', 'size="6" maxlength="30" style="width: 100px" value="' . HEADER_SEARCH_DEFAULT_TEXT . '" onfocus="if (this.value == \'' . HEADER_SEARCH_DEFAULT_TEXT . '\') this.value = \'\';" onblur="if (this.value == \'\') this.value = \'' . HEADER_SEARCH_DEFAULT_TEXT . '\';"') . ' ' . zen_image_submit (BUTTON_IMAGE_SEARCH,HEADER_SEARCH_BUTTON);
} else {
$content .= zen_draw_input_field('keyword', '', 'size="6" maxlength="30" style="width: 100px" value="' . HEADER_SEARCH_DEFAULT_TEXT . '" onfocus="if (this.value == \'' . HEADER_SEARCH_DEFAULT_TEXT . '\') this.value = \'\';" onblur="if (this.value == \'\') this.value = \'' . HEADER_SEARCH_DEFAULT_TEXT . '\';"') . ' <input type="submit" value="' . HEADER_SEARCH_BUTTON . '" style="width: 45px" />';
}
Add '<span class="searchHeaderTextField">' . and </span> in two places to get
PHP Code:
if (strtolower(IMAGE_USE_CSS_BUTTONS) == 'yes') {
$content .= '<span class="searchHeaderTextField">' . zen_draw_input_field('keyword', '', 'size="6" maxlength="30" style="width: 100px" value="' . HEADER_SEARCH_DEFAULT_TEXT . '" onfocus="if (this.value == \'' . HEADER_SEARCH_DEFAULT_TEXT . '\') this.value = \'\';" onblur="if (this.value == \'\') this.value = \'' . HEADER_SEARCH_DEFAULT_TEXT . '\';"') . '</span> ' . zen_image_submit (BUTTON_IMAGE_SEARCH,HEADER_SEARCH_BUTTON);
} else {
$content .= '<span class="searchHeaderTextField">' . zen_draw_input_field('keyword', '', 'size="6" maxlength="30" style="width: 100px" value="' . HEADER_SEARCH_DEFAULT_TEXT . '" onfocus="if (this.value == \'' . HEADER_SEARCH_DEFAULT_TEXT . '\') this.value = \'\';" onblur="if (this.value == \'\') this.value = \'' . HEADER_SEARCH_DEFAULT_TEXT . '\';"') . '</span> <input type="submit" value="' . HEADER_SEARCH_BUTTON . '" style="width: 45px" />';
}
Then you can style
.searchHeaderTextField {position: relative; bottom: 1px;}
or whatever makes it align properly.