You should follow these instructions if you see a warning like this on the WeBWorK:
Follow the link in the warning or click here.
Scroll down the page and click on the Download the TeX fonts link.
Click the TeX-fonts.zip link to download the zip file containing the fonts.
When asked what to do with the file, choose Open.
NOTE: These instructions are for Windows XP. If you cannot follow these exactly you will have to extract the folder to C:\temp\ manually.
When the compressed folder's window opens, press the Extract all files button on the left side.
The compressed folder extraction wizard should start. Simply press Next.
Change the output folder to "C:\temp\" and then press Next.
Uncheck Show extracted files if necessary and press Finish.
Choose Start > Settings > Control Panel
Note: In Windows XP, choose Start > Control Panel
Double-click the Fonts folder.
Choose File > Install New Font.
In the Drives list, select the C: drive.
In the Folders list, navigate to "C:\temp\TeX-fonts\", the folder where the jsMath fonts were extracted.
Select all of the jsMath fonts. Either press the Select All button or hold down the CTRL key and click each font.
Make sure the Copy fonts to the Fonts folder check box is selected.
Click OK to install the fonts.
You can now close the Font folder's window.
Make sure that you restart your web browser so that it can detect the new fonts.
You can now delete the extracted files in "C:\temp\TeX-fonts\", though this is not necessary.
That's it! You should no longer see the jsMath warning on the WeBWorK pages.