Question

I have a div called main which is 100% width of his parent width.
In #main I have input field and textarea.

I can expand input field (width:100%) but how to do the same with textarea ?

Answer 1

Do not use the width attribute. Use css instead. You can put the style in a separate css file:

input, textarea { width: 100%; }

or you can put the style inline in the elements:

<input type="text" style="width: 100%" />
<textarea style="width: 100%"></textarea>

I recommend the first option because it allows you to separate the style of the page.