SmartPhone problem on the form

SmartPhone problem on the form

I create a contact form and embed it successfully to my website.
The problem is when I use my android (2.3.3) phone browser to access to the form, The captcha field doesn't display.
Try with Firefox and Opera browser on my phone, The captcha field is Ok, but when I click on submit, the screen stops forever at "Please wait...." text.
There is no problem when accessing by desktop computer.
Any one is facing this problem? Your help would be appreciated.