I’ve written very simple jQuery plugin which prevents user from entering non-numeric values to input field. It is available on Github.
Allowed values are “0-9 + – , .”
//Example of use $('input').numberField();
Live DEMO here
Update: It was not possible to write numbers on czech keyboard in a way like “Shift+š”. Fixed now.
Credits: Jiří Knesl and his ESCR script. People from Slovakia might use his LSCR script useful 🙂