Dennis Bratcher, Old Testament scholar of CRI/Voice Institute writes,
"We are accustomed to reading the Bible backwards. That is, we have tended to assume that the New Testament provides all the clues we need to understand the Old Testament. As a result, we tend to read the Old Testament in light of what we understand about the New Testament. However, most of the time we are not really even reading the Old Testament in light of the New Testament. We are actually reading the Old Testament in light of much later highly developed doctrines and systematic theology seen through the eyes of 21st century Western perspectives. We tend not to take seriously the deep roots that most of the New Testament has in the thought world, symbolism, and theology of the Old Testament."
read more in his article on Immanuel in Isaiah and Matthew and Isaiah 7:14: Translation Issues
For a Jewish view of Isaiah 7:14, see this article from Messiah Truth which gives a different perspective on the whole issue.