The selected column in the table above could not be properly selected because of the misaligned cell.
Tables are all about precision — which is a large part of what makes them easy to use. When that precision gets thrown off, the table can become much more complicated to format or edit.
When cells are sized individually, as shown in the illustration, editing the table can be frustrating and the result might not look as good as it could. The ability to format entire columns or rows at one time helps you keep table formatting consistent, precise, and easy-to-manage.
You may have resized cells accidentally by selecting them before dragging to resize columns. Keep in mind that it is not necessary to select a column or a row before dragging its edge to resize it. If just some cells in a column are inadvertently resized, undo the action (to do this, press CTRL+Z or, on the Edit menu, click Undo), correct your selection, and size the column again.
If the alignment of your table content appears to be inconsistent, or you are unable to select an entire, single column at once, check for misaligned cells.