How to Prevent Wide Text Boxes from Extending Beyond Their Containers?

Preventing Wide Text Boxes from Overextending Containers

When attempting to create a text box that spans the entire width of a container, a common issue arises: the actual width of the text box may extend beyond the container's boundaries. This is because browsers allocate margin, border, and padding by default, which effectively increases the text box's overall width.

Consider the following example:

<code class="html"><div id="outer">
  <div id="inner">
    <input type="text" class="wide" />
    <input type="text" class="normal" />
    <div style="clear:both;"></div>
  </div>
</div></code>

<code class="css">#outer {
  border: 1px solid #000;
  width: 320px;
  margin: 0px;
  padding: 0px;
}
#inner {
  margin: 20px;
  padding: 20px;
  background: #999;
  border: 1px solid #000;
}
input.wide {
  display: block;
  margin: 0px;
  width: 100%;
}
input.normal {
  display: block;
  float: right;
}</code>

In this scenario, the "wide" class text box extends beyond the container, whereas the "normal" class text box aligns precisely with the container's edge. To prevent overextension, the "box-sizing" property introduced in CSS3 provides a solution.

<code class="css">input.wide {
  display: block;
  margin: 0px;
  width: 100%;
  box-sizing: border-box;
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
}</code>

By setting "box-sizing" to "border-box," the width of the text box is defined to include external padding and borders. This ensures that the text box occupies the full width of its container without extending beyond its boundaries.

Unfortunately, as "box-sizing" is a CSS3 property, browser compatibility may vary. As the specification process is ongoing, browsers have adopted different temporary names for it: "moz-box-sizing" for Mozilla and "webkit-box-sizing" for WebKit-based browsers.

An alternative approach for older browsers involves applying "padding-right" to the parent element (e.g., a "div" or "td"). This can help accommodate the additional space occupied by default padding and borders in the input element. However, the amount of "padding-right" required may vary depending on the browser used.

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