In Microsoft Excel, green triangles indicate possible errors in the contents of a cell. Red triangles indicate the presence of user comments in the worksheet cell. The green triangle appears in the upper-left corner of a cell, while the red triangle appears in the upper-right corner of a cell. Here's how these indicators work and how you can change their default settings.
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The green triangle appears in a cell when the contents of the cell violate one of Excel's error checking rules.
These rules are enabled by default and check for common errors, such as cells with formulas that evaluate to an error such as #VALUE! or #DIV/0!; formulas that are inconsistent or different from formulas in surrounding cells; and numbers formatted as text data.
When you select a cell with a green triangle, the Error Options button appears next to it. The Error Options button is a yellow diamond with a gray square background. It provides options for correcting the observed error.
