` to disable all the controls within.
{% example html %}
{% endexample %}
Caveat about link functionality of `<a>`
Our styles use `pointer-events: none` to try to disable the link functionality of `<a class="btn btn-*">` buttons in this case, but that CSS property is not yet standardized and isn't fully supported in Opera 18 and below, or in Internet Explorer 11. So to be safe, use custom JavaScript to disable such links.
Cross-browser compatibility
While Bootstrap will apply these styles in all browsers, Internet Explorer 9 and below don't actually support the `disabled` attribute on a `<fieldset>`. Use custom JavaScript to disable the fieldset in these browsers.
## Readonly inputs
Add the `readonly` boolean attribute on an input to prevent user input and style the input as disabled.
{% example html %}
{% endexample %}
## Validation
Bootstrap includes validation styles for error, warning, and success states on form controls. To use, add `.has-warning`, `.has-error`, or `.has-success` to the parent element. Any `.control-label`, `.form-control`, and `.help-block` within that element will receive the validation styles.
{% example html %}
Input with success
Input with warning
Input with error
{% endexample %}
You can also add optional feedback icons with the addition of `.has-feedback` and the right icon.
Icons, labels, and input groups
Manual positioning of feedback icons is required for inputs without a label and for input groups with an add-on on the right. You are strongly encouraged to provide labels for all inputs for accessibility reasons. If you wish to prevent labels from being displayed, hide them with the `sr-only` class. If you must do without labels, adjust the `top` value of the feedback icon. For input groups, adjust the `right` value to an appropriate pixel value depending on the width of your addon.
{% example html %}
Input with success
Input with warning
Input with error
{% endexample %}
{% example html %}
{% endexample %}
{% example html %}
{% endexample %}
For form controls with no visible label, add the `.sr-only` class on the label. Bootstrap will automatically adjust the position of the icon once it's been added.
{% example html %}
Hidden label
{% endexample %}
## Control sizing
Set heights using classes like `.input-lg`, and set widths using grid column classes like `.col-lg-*`.
{% example html %}
...
...
...
{% endexample %}
Quickly size labels and form controls within `.form-horizontal` by adding `.form-group-lg` or `.form-group-sm` to existing `.form-group`s.
{% example html %}
{% endexample %}
## Column sizing
Wrap inputs in grid columns, or any custom parent element, to easily enforce desired widths.
{% example html %}
{% endexample %}
## Help text
Block level help text for form controls.
{% example html %}
A block of help text that breaks onto a new line and may extend beyond one line.
{% endexample %}