Looks like the Great Firewall or something like it is preventing you from completely loading www.skritter.com because it is hosted on Google App Engine, which is periodically blocked. Try instead our mirror:
This might also be caused by an internet filter, such as SafeEyes. If you have such a filter installed, try adding appspot.com to the list of allowed domains.
Authorized by Hanban, HSK Standard Course is developed under the joint efforts of Beijing Language and Culture University Press and Chinese Testing International (CTI). With HSK test papers as its primary source, HSK Standard Course is characterized by a humorous style, familiar topics and a scientific course design.
This is Textbook 1, which includes 15 lessons and covers 150 words and 45 language points required by the HSK Level 1 test. Upon finishing this book, students will be able to 'understand and use a few simple Chinese words and sentences to meet their specific needs in communication and to prepare themselves for further learning'.