Final answer:
Zeros found at the beginning of a decimal number, known as leading zeros (as in 0.00439), are not considered significant digits and are simply placeholders for the decimal position.
Step-by-step explanation:
Zeros in front of whole numbers, like in the number 0.00439, are called leading zeros. These zeros are not significant digits; they are merely placeholders that establish the decimal position. Significant digits are the numbers that carry meaningful contributions to its precision. Leading zeros do not count as significant because they do not represent a measured or estimated value, but are only used to position the significant figures correctly.