HTML input textbox with a width of 100% overflows table cells

Question

Does anyone know why the input elements with a width of 100% go over the table\'s cells border.

In the simple example below input box go over the table\'s cells border,

Answer 1

The problem has been explained previously so I will only reiterate: width doesn't take into account border and padding. One possible answer to this not discussed but which I have found helped me out a bunch is to wrap your inputs. Here's the code, and I'll explain how this helps in a second:

The DIV wrapping the INPUT has no padding nor does it have a border. This is the solution. A DIV will expand to its container's size, but it will also respect border and padding. Now, the INPUT will have no issue expanding to the size of its container since it is border-less and pad-less. Also note that the DIV has its overflow set to hidden. It seems that by default items can fall outside of their container with the default overflow of visible. This just ensures that the input stays inside its container and doesn't attempt to poke through.

I've tested this in Chrome and in Fire Fox. Both seem to respect this solution well.

UPDATE: Since I just got a random downvote, I would like to say that a better way to deal with overflow is with the CSS3 box-sizing attribute as described by pricco:

.myinput {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    -ms-box-sizing: border-box;
    -o-box-sizing: border-box;
    box-sizing: border-box;
}

This seems to be pretty well supported by the major browsers and isn't "hacky" like the overflow trick. There are, however, some minor issues on current browsers with this approach (see http://caniuse.com/#search=box-sizing Known Issues).