Mathematics is a discipline with a specialized notation. In the days when the pencil or pen was the tool of choice this meant coming to an agreement about how to "properly" write an expression to avoid ambiguity and miscommunication.
However with the advent of typewriters and computers the conventions previously arrived at have turned out to be very difficult to transcribe onto paper or the screen.
I am making (almost) all of my notes as web pages. In order to capture the notational complexities I use a combination of two different software packages. I begin by using Dreamweaver to create my basic web page. However when I encounter a mathematical expression that is difficult to express in Dreamweaver I switch to Microsoft Word which has been extended with the software package MathType 5. It is relatively easy to compose the mathematical expression using MathType, then save the result as an image (i.e. a gif file) and then paste this image into the Dreamweaver file. This actually sounds more complicated that it is in practice. Creating the expression is straightforward (once one becomes familiar with MathType - which is easy) and the saving and retrieving of the image is just a few mouse clicks).
Here is an example: