I'm a complete CSS novice -- my background is back-end development. So please forgive the ignorance in advance.
I'm attempting to learn a bit more about the application (or.. practical use) of CSS.
Given the following CSS:
<input type="text" placeholder="Search" class="input-size">
What you have is correct, however you do not have padding defined in your new class. What is most likely happening is that padding is defined for
input and it just inheriting the properties from the default style. Since you have it inspected - trace the margin rule.