Finding that your html layouts are fine in all clients except on your iPhone? This may be due to text size.
The iPhone and iPad mail client only display text at 13px or higher. If you have specified a lower value than this, the text will be displayed at 13px.
It seems that Apple has done this in order to make emails easier to read on their portable devices however a 1px change can really make an HTML layout look terrible. Text such as disclaimers & fine print really don’t need to be this large, particulary since it’s so easy to zoom in on the mail application.
To prevent your fonts from being resized, you can use this style (inline or header are fine):