<p>Can I somehow disable spell-checking on HTML textfields (as seen in e.g. Safari)?</p>

Update
: As suggested by a commenter (additional credit to
How can I disable the spell checker on text inputs on the iPhone
), use this to handle all desktop and mobile browsers.
```
```
<tag autocomplete="off" autocorrect="off" autocapitalize="off" spellcheck="false"/>
```
```
Original answer: Javascript cannot override user settings, so unless you use another mechanism other than textfields, this is not (or shouldn't be) possible.