
  Width and height control element size.
  
  ## Fixed width (danger)
  ```css
  .box {
    width: 500px;
  }
  ```
  
  Breaks on mobile.
  
  ## Flexible width (best)
  ```css
  .box {
    width: 100%;
    max-width: 500px;
  }
  ```
  
  ## Height
  Avoid fixed height unless necessary.
  
  ## Real world advice
  - Let content decide height
  - Control width carefully
  
  ## Remember
  - max-width saves responsive layout
  - Fixed sizes cause problems
  

Learn how width and height really work, including percentages, max-width, and why fixed sizes break layouts.

CSS Width and Height

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CSS Width and Height

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