You receive a "Too many different cell formats" error message in Excel

In Microsoft Excel 2003, when you format a cell or a range of cells, you may receive the following error message: 


In Microsoft Excel 2007/2010 files may produce the following error message;


Other scenarios that as associated with styles are:

This problem occurs when the workbook contains more than approximately 4,000 different combinations of cell formats in Excel 2003 or 64,000 in Excel 2007 and higher. A combination is defined as a unique set of formatting elements that are applied to a cell. A combination includes all font formatting (for example: typeface, font size, italic, bold, and underline), borders (for example: location, weight, and color), cell patterns, number formatting, alignment, and cell protection.

NOTE: If two or more cells share exactly the same formatting, they use one formatting combination. However, if there are any differences in formatting between the cells, each cell uses a different combination.

In Excel style counts may increase when copying between workbooks because custom styles are copied.

A workbook that has more than 4,000 styles may open in Excel 2007 and higher (because of the increased limitation for formatting) but result in an error in Excel 2003.

1. To prevent styles from built in styles from being duplicated when copied make sure you have the latest updates for Excel installed from Windows Update. 

2. The following KB articles allow disabling copying custom styles between workbooks in one instance of Excel. Install and add registry key in the following article. 



3. To cleanup workbooks that already have numerous styles, run one of the following:


4. Simplifying the formatting in your workbooks. For example, the following are suggestions for simplifying formatting: 

• Use a standard font. Using the same font for all cells reduces the number of formatting combinations.
• If you use borders in a worksheet, use them consistently.
  
  NOTE: If you apply a border to the right side of a cell, it is not necessary to apply a border to the left side of the cell that is to the right because the borders overlap.
• If you apply patterns to the cells, remove the patterns by clicking No Color in the Patterns tab of the Format Cells dialog box.
• Use Styles to standardize the formatting used throughout the workbook.

NOTE: After you simplify or standardize the formatting in the workbook, save, close, and then reopen the workbook before you apply additional cell formatting.

In most cases, the limit of approximately 4,000 different formatting combinations for a single workbook is sufficient. This problem is likely to occur only when the workbook contains a large number of worksheets that use different formatting, or when a large number of cells are all formatted differently.