I have read the following which is from Best Practices for Encoding Video with the VP6 Codec on the Adobe website here - http://www.adobe.com/devnet/flash/articles/encoding_video_print.html. It is talking about common video ratios (320x240, 640x480)

Although these ratios are standard, and should be used to avoid distorting the video, the size of the encoded video is not set in stone. The original web video sizes used heights and widths that were evenly divisible by 16. This was mandatory for many early codecs. Although this is not necessary for modern codecs, you should stick to even heights and widths.

What do they mean by 'even heights and widths'. I am thinking about encoding my video at 400x300 to make it slightly bigger, this is still 4x3 format but should I just stick at 320x240 and resize it on the screen? Clearly there are benefits to this in terms of storage size and delivery costs.

In some places on my site I want to show the video at 400x300 but in others I want it to play full screen so this is why I am wondering if a larger original size (400x300) will give better results when blown up.

Any thoughts?