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.
The Elementary Comprehensive Course (I), with altogether 30 lessons, is suitable for total beginners or beginners who can communicate in the simplest Chinese.
Developing Chinese: Elementary Comprehensive I (发展汉语初级综合). 2nd Edition. Published 2011. Written by Rong Jihua. 350 pages. ISBN: 9787561930762.