WML services can support both push and pull transactions. Pull transactions transmit information in response to a user request. The design of WML decks requires special considerations due to a few distinct limitations. First, handheld devices have a smaller screen size and resolution. A cell phone may only have a few lines of textual display, with each line containing eight to 12 characters.
Models vary in window display size.
Second, cellular phones have a numeric keypad and several additional function keys. A more sophisticated device may have software-programmable buttons, but there are no keyboards or mice in the wireless world. Third, handheld devices and cellular phones have limited computational resources. The low-power CPU and small memory size of these devices are often limited by power constraints. Finally, you have to deal with narrow-bandwidth connectivity.