Panels total width adds to only 99%

I have this problem too.

EDIT: see http://groups.drupal.org/node/19298

hefox is correct. IE has serious bugs regarding width and float, and the only solution I've found is to lock things to 99%. This has had some minor side effects here and there, but it is what we have.

If you need better than that, you will have to design your own layouts, or we need to implement a flexible system that uses a more robust method.

Why you make all suffer by unused IE6 support?

Why just not to use CSS hack:
panels\plugins\layouts\flexible\flexible.inc

      // Because we love IE so much, auto scale everything to 99%. This
      // means adding up the actual widths and then providing a multiplier
      // to each so that the total is 99%.
      $scale = $renderer->scale_base / $middle_total;
      foreach ($middle as $position => $id) {
        $class = "." . $renderer->base[$type] . "-$id";
        $ie_class = "* html ." . $renderer->base[$type] . "-$id";
        $css[$class] = array(
          'float' => 'left',
          'width' => number_format($renderer->settings['items'][$id]['width'], 4, '.', '') . "%",
        );
        $css[$ie_class] = array(
          'float' => 'left',
          'width' => number_format($renderer->settings['items'][$id]['width'] * $scale, 4, '.', '') . "%",
        );

works for me.

Seriously? You reopened an issue and changed stuff around over a year later? Open a new issue.

What the purpose to open same issue ticket? To close it as duplicate?

Issue is still here.

Found proper checkbox when editing reused layout in canvas settings:
Scale fluid widths for IE6

This should be re-opened for version 7 as well. I see this is an OLD "will not fix." The problem is, it should only be affecting the widths, if and when IE6 is the browser. But it doesn't do that, it affects the widths of panels regions even if you are in the latest version of Chrome or Firefox or Safari. Thats why it should be an open issue.