Alter Page With OnClick()?

I need to display some addition html within a form when a checkbox is clicked. I know nothing about javascript but am pretty sure we can do it.

Here is what the code will look like if the box is NOT checked:

HTML Code:

<tr><td><input type="checkbox" name="name1" value="yes"> Check Me!</td><td>&nbsp;</td></tr>
However when the box is checked, I want some additional HTML to show, like this:

HTML Code:

<tr><td><input type="checkbox" name="name1" value="yes"> Check Me!</td><td><input type="text" value=""> Text Box Here!</td></tr>

Basically, when the checkbox is clicked, I want a text area to appear.