This is a slow device running an ancient version of  Windows Mobile. You'll have to treat it with kid gloves and say "please". Don't get mad if every once in a while the device seems to hum "The Macarana", because that's about how old it is. Indulge it's whim.

Are you using jQuery Mobile? If so, the first thing you should do is not. Something more simple would be appropriate, perhaps Bootstrap or some other all-or-mostly CSS solution.

Are you making use of Ruby programming, or only using Javascript? On any device, Ruby code is generally going to be faster than Javascript. And you will likely face fewer memory issues with Ruby than Javascript. If you are writing in Javascript because you want to avoid learning Ruby, this is not the device to do that with. It needs the performance that Ruby can bring. Javascript should be reserved for truly "front-end" stuff - dealing with browser events and UI only.

If you ARE using jQuery Mobile (but don't) be aware that using WebView.navigate does a full reload of all of your CSS/JS which can be costly. If you ARE using jQuery Mobile (but don't) navigate using JS $.mobile.changePage().

If you give us some more specific details, we can offer more concrete suggestions

Some devices can have some delay issue with "click" events. This affects mostly iPhone, and is generally solved for modern Android devices. Dunno about Windows Mobile 6.5 though! It may be advantageous to use a different event. In jQuery Mobile (but don't!) you could use vclick to bypass the "click delay", otherwise you need to use a combo of touchstart and mousedown (if this thing has touch). Unclear if this possible 300-400mSec delay is part of your problem or not.

Hi Mazen

Will the videos under the section "Performance" can help you https://developer.motorolasolutions.com/community/rhomobile-suite/videos ?

Thank you.
Visnupriya R
Kutir Mobility