The Half-Life Saga Story Guide is an informative fansite dedicated to providing a simplified explanation of the events of the Half-Life and Portal series in chronological order.
The project was created by interface designer Chan Karunamuni (who currently works for Apple Inc.) between 2003 and 2007 with help from readers and contributors from other community sites such as the Steam Users’ Forums.
A lot of the content on there is speculative in nature. I wouldn’t set much store by it.