iOS devices add a lot of annoying styles on form inputs, particularly on input[type=submit]. Shown below are the same simple search form on a desktop browser, and on an iPad
The version I had working is:
input {
-webkit-appearance: none;
}
In some webkit browser versions, you may also be faced with the border-radius still being in place. Reset with the following:
input {
-webkit-border-radius:0;
border-radius:0;
}
This can be extended to apply to all webkit styled form components such as input, select, button or textarea.
In reference to the original question, you wouldn't use the value 'none' when clearing any unit based css element.
Also be aware that this hides checkboxes in Chrome, so perhaps use something like input[type=text] or input[type=submit], input[type=text] or instead filter out those that don't use rounded corner settings such as input:not([type=checkbox]), input:not([type=radio]).