These are the old Nick Jr websites from 1999-2015, aka the hallmark of

1999-2000 Nick Jr Website

2000-2004 Nick Jr Playtime

2004-2009 Nick Jr Playtime

2009-2010 Nick Jr Playtime

2010-2015 Nick Jr Kids Website (RNS Edition)

Noggin Websites

2004 Noggin Website

2007-2009 Noggin Website

Credit to Nostalgivault, Raymond Haun, ThatDoraGuy (Formerly Dora&WubbzyFTWPawPatrol&BabySharkFTL), Co M 88, Molly from Bubble Guppies, and Rare Noggin Stuff.