Ok. So I made a flcker account and uploaded two photos. How do I get the display size link?
Well... Here's where it gets a little tricky. -Sorry.
If you're happy with Flickr's default size, then...
1) Make sure you have the picture you want to display/link on your screen.
2) Click on "Share This" which appears in the upper right part of the window.
3) For other sites, you can actually just click on either "Grab the link", "Grab the HTML" or "Blog it" in order to link/post your photo on another site. However, for HHW...
4) Click on "Grab the HTML".
5) In the "stuff" that pops up, look for "<img src=""
6) Select/highlight the "stuff" from "http://" to ".jpg"
7) Copy the "stuff" you selected. That is the direct link to the photo in Flickr's files.

To post the pic here on HHW, use the IMG tags, and place the link you copied between them.
It's a little convoluted, but... You could always go back to PhotoBucket and use the Edit-.Resize commands over there.
