You have to insure that the users have all the necessary software they need in order to use the instructional materials without obstruction.   That is especially the case if we are in a familiar and controlled environment, like computer rooms at faculties.

Recommendations for the selection of software can be found at the CARNet Referral Center for the Selection of Courseware tools, Computer Support and Software for the use of IT in education.
 
The strategy of low technologies can be used again for web-based instructional materials available to a wide range of unknown users. For example, you can presuppose that the users will not be using the latest Windows version. Most of the users use such platform.

Freeware sources should be offered at the homepage for all the additional programs not included in the standard version of a program platform. Most of the products offer such sources, but if they cannot be found, it is better to use a different program.
 
The computer equipment makers' strategy is to make old equipment obsolete and incompatible as fast as possible (usually within 4-5 years) in such a way that the older models cannot read the new products that appear on the market. That is the approach which ensured the computer companies secure profits, but makes life difficult for all who are trying to make products for a broad range of unknown users.  

 
IEEE decided to use web based education. On their sites they provide links to programs necessary for normal viewing of all the examples.

 

Links to examples we used:

IEEE Virtual Museum (there are links to programs that are necessary in order to see all the examples)