Constructing a JavaScript slide
Your questions seem to have been answered (use jQuery), so here are a couple of small points regarding readability:


be consistent with your variable names (eg sliderImg vs flickrImgs: one is plural, one singular, and in the rest of the code, you mainly use flickrX, except for the sliderImg one; I would prefer sliderX everywhere, because it doesn't seem to matter where the images come from).
some variable names could be a lot better. Eg when reading flickrImgs/sliderImg I'm thinking it's an array of images (or image paths/names). But they are not, they are integers, so I would prefer imageCount/imageSize, and currentSliderPosition. flickrDisplay on the other hand seems to actually be a collection of images, so sliderImages would probably be a good name for it.
your indentation is off, which decreases the readability of your code.
your comments aren't all that helpful. NOW AND NEXT FUNCTION/SLIDE TRANSITION aren't really necessary, and For each loop incrementing each slide by one doesn't really help either (because that's exactly what the code already told me; If you do want to add a comment, it would be more helpful to explain what it means when a slide is increased.
use curly brackets even for one line statements to increase readability and to possibly avoid bugs.
visiable isn't a valid value for visibility, you probably meant visible.