You can make the button disabled, by using the disabled attribute of the <input> tag, but to make the button invisible you need to use CSS (presumably you want to make it visible later?)

<input style="visibility:hidden;" type="button" value="Hello world!" disabled>

If, however, you simply want to make the form control hidden - you don't want the end user to ever have control over the element, then consider using

type="hidden"

. Although this is not a button!?

To style the button in other ways, you need to use CSS. (Perhaps/preferebly with an external stylesheet.) Using an inline style in this case...

<input style="background-color:#ccf;" type="button" value="Hello world!">

Will give the button a light blue (#ccf) background.

Thanks a lot

It might be helpful to note that buttons in themselves are worthless without Javascript or some other client side programming. Inherently they don't do anything. That being said, if Javascript (or other client-side programming) is disabled, they still . . . won't do anything. :-)

So if your intent is to disable the button to avoid double-clicks, use a submit button instead. This will still allow Javascript-disabled browsers to use your button:

<form>
<input type="submit" onClick="this.disabled=true;" value="Submit">
</form>

Thanks for your suggestion.

This is another choice for me.