What are the limitations of mixed content elements? Under what circumstances should you not use them?

What will be an ideal response?

Because they are very flexible, elements with mixed content do not add much defined structure to a document. You can specify only the names of the child elements, and you cannot constrain the order in which those child elements appear or control the number of occurrences for each element. An element might contain only text or it might contain any number of child elements in any order. For this reason, it is best to avoid working with mixed content if you want a tightly structured document.