Why is My Dropdown Menu Hidden Behind My Input Field in IE7?

IE7: Understanding the Z-Index Layering Confusion

IE7 presents complexities in the application of z-index for element layering. Understanding how z-index works can help resolve layering issues effectively.

Z-Index and Stacking Contexts

Contrary to its name, z-index is not an absolute measure. Elements with a higher z-index can be hidden behind elements with a lower z-index if they belong to different stacking contexts.

A stacking context is created for positioned elements (absolute, relative, or fixed). However, IE7 mistakenly interprets positioned elements without z-index as creating new stacking contexts.

The Problem in Your Code

In your example, you have a positioned span (<span>) that lacks a z-index. IE7 interprets this as creating a new stacking context, making the dropdown menu (

) hidden behind the input field ().

Possible Solutions

To fix the issue, consider the following solutions:

1. Add z-index to the Positioned Span:

#envelope-1 {
  position: relative;
  z-index: 1;
}

This explicitly defines the stacking context and ensures the dropdown overlaps the input field.

2. Remove Position from the Span:

<span>

By removing the position, you eliminate the unnecessary stacking context. The elements will now follow the default layering order, where the dropdown is positioned above the input field.

Additional Considerations

• Z-index only affects elements within the same stacking context.
• IE6 has an additional bug where select boxes and iframes always float on top of everything else.
• For a more detailed explanation and a similar bug example, refer to: https://www.brenelz.com/blog/2009/02/03/squish-the-internet-explorer-z-index-bug/

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