How to refer to a tag in CSS

In CSS, the space character on its own means “descendant”. For example, this refers to every td that is a descendant of table#cooltable:

table#cooltable td {
    ...
}

You can also use the > operator: this is more strict, and only applies to direct children. To achieve the same effect using this, you would write:

table#cooltable > tr > td {
    ...
}