Body height 100% displaying vertical scrollbar

Decoding the margin collapse

Margin collapse is a CSS phenomenon where adjacent vertical margins combine to form a single margin equal to the greatest individual margin. This seemingly innocuous behavior can cause shift in content and potentially introduce unexpected scrollbar appearance, as it doesn't add to the height dimensions.

Mastering height with calc

The CSS function calc() allows precise adjustment of element height, keeping in mind the margins. Set your #container's height with a correct offset:

#container {
  height: calc(100% - 20px); /* Assume we have a 20px margin, because assuming makes an "ass" of "u" and "me" */
}
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This results in your container fitting within the body without causing overflow due to margins.

The art of resetting

Resetting CSS helps avoid unexpected layout surprises. Here's how one can do it:

• Normalize.css can help establish cross-browser consistency.
• Using a universal selector, you can erase default margins and paddings across all elements.
• You could also individually neutralize default margins and paddings on particular elements needing specific styles.

Controlling overflow

Sometimes, you might want some elements to slide off the viewport without causing a scrollbar. Here's how you manage it:

.overflow-hidden {
  overflow: hidden; /* Overflow? More like "over and out!" */
}
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Be careful though, as this could reduce content accessibility.

Flow and positioning

Avoid absolute positioning and maintain document flow instead. For center alignment:

.centered-container {
  margin-left: auto;
  margin-right: auto;
  width: 50%; /* Just like my coffee cup, half full or half empty? */
}
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Effectively manage the float property to avoid layout disruption, and zero out margins and padding to avoid float-induced unexpected behaviors.

Browser compatibility checks

Remember that older browsers may not support calc(). Do check Can I use to verify its compatibility with your target browsers.