Figure 1.45. Selecting even-indexed p elements with :nth-last-of-type(even)Ifthisstillseemsfuzzy,playwithPaulMaloney’sNth-Testtool,^17 orviewtheex-
amplesatNthMaster.^18 Bothprojectsareexcellentwaystolearnmoreaboutthese
pseudo-classes.Styling Form Fields Based on Input
Let’stakealookatsomepseudo-classesthatarespecifictoformfieldsandform
fieldinput.Thesepseudo-classescanbeusedtostylefieldsbasedonthevalidity
ofuserinput,whetherthefieldisrequiredorcurrentlyenabled.Allofthepseudo-classesthatfollowarespecifictoforms.Asaresult,there’sless
ofaneedtolimitthescopewithaselector.Using:enabledwon’tintroduceside
effectsforspanelements.Limitingthescopeishelpful,however,whenyouwant
tosylevarioustypesofformcontrolsdifferently.:enabled and :disabled
Astheirnamesuggests,thesepseudo-classesmatchelementsthathave(orlack)the
disabledHTML5attribute.Thiscanbeaninputcontrolsuchasinput,select,or
buttonelement(seenshortly),oritcanbeafieldsetelement:(^17) http://nth-test.com/
(^18) http://nthmaster.com/
62 CSS Master