I find more often than not that the average user really struggles with the default html <select> field when in multiple selection mode.
Half of me thinks, it’s a standard control, people should learn to use it and/or read instructions regarding ctrl+click. The other half then realises, the control itself has – quite frankly – exceptionally poor usability and accessibility. My experience would show that if a user has to learn a website, it’s unlikely they will stick around long enough for you to get any decent ROI, so it’s essential that this control be replaced with something more practical, with a fallback to the default for browsers that don’t support the usable one.
Step in jQuery… I’ve done quite a bit of searching around on this one, and the tool that wins hands down time and time again is the jQuery UI Multiple Select Widget by Eric Hynds. It looks great, works great and replaces the standard control with something that’s a no brainer to use.
