The format of a valid css selector is defined by the W3C standards. To put it short you have to follow this syntax for the tsuiseki tracking module: element.classname

Examples

All links that have the class foo:

a.foo

All input fields (e.g. buttons) having the class bar:

input.bar

All links that have the class foo plus all links that have the class bar:

a.foo, a.bar