When a reader looks at a page that contains mathematics, jsMath will try to render that mathematics using the TeX fonts if they are available on the reader's computer. If not, it will fall back on images of the characters in the TeX fonts. These images are stored on your server, so they are always available to the user regardless of what fonts he or she has installed locally.
Using jsMath without Image Fonts
This method, however, requires that you have loaded the image fonts onto your server where jsMath can access them. Because the image fonts comprise thousands of small image files (one for each character in each font in each size), these can take considerable space on your server (on the order of 80MB), and you may not wish to expend that amount of space. (For example, you may be making a stand-alone CD that uses mathematics, and you can't afford to use 80MB of the disk for images.)
It is possible to install jsMath without these image fonts, if you need to conserve disk space. To do this, include
in your web page before loading
Note that if you do this, however, your readers will not be able to select the image-font or symbols-only fallback methods, and so they will be forced to use the unicode fallback method if they haven't installed the TeX fonts. While jsMath tries hard to make unicode mode work, it is not as reliable as the image-based fallback, since it is dependent on the fonts available on the user's system, and there is no guarantee that there are any unicode fonts available. If at all possible, you should make the image fonts available when you install jsMath.