The HTML5 Canvas Text API - HTML5 Canvas - page 96

Also, don't forget the event listener for the textAlpha range control:
formElement = document.getElementById("textAlpha");
formElement.addEventListener('change', textAlphaChanged, false);
The results will look like Figure 3-7 .
Figure 3-7. Text with globalAlpha applied
Global Shadows and Text
HTML5 Canvas includes a unique set of properties for creating a shadow for drawings.
The context.shadow functions are not unique to text, but they can make some very good
text effects with very little effort.