This page will display general information about a kanji such as its readings and stroke count, and show an image of the kanji rendered in seven different styles (provided the fonts for these styles support the character requested.
The information has backlinks to the dictionary so that you can search for words that contain the looked up kanji in some way, and also gives you the compositional parents and children for the character, which you can browse through. Not all characters that are found in the graphical relations exist in the Japanese character set, so for some of these there will simply be no useful kanji information, although for a reasonably number there is at least a print form, so you won't get a broken image link. If you do get a broken image link, the character is either not a character (such as a rare variant of a component radical) or it's found somewhere deep in the unicode "CJK ideographs, extension A" or "B" blocks, which cover 49293 characters that you will not find in any normal Japanese font. I highly recommend that you install the HAN NOM fonts (HAN NOM A and HAN NOM B) which are free, to be able to even see these characters in your browser (or other program).
The images are generated using PHP+GD. GD lacks a wrapper method for FreeType2 's 'get char index' method, which tells you whether or not a particular font supports a particular glyph, so a custom OTF/TTF parser was written to analyse font files for whether or not they support glyphs, based on the OpenType file layout specification. The images generated are encoded as bitmap image as GIF, which are quite small (<10kb per image). While it would be quite nice to generate SVG images instead, handing people the actual font's vector data would allow someone to perfectly reverse engineering the fonts that were used... and that wouldn't be very good =)
The server's version of GD/FreeType is not the most recent one, and will misalign some characters, so for all kanji that can be found in kanjidic/kanjidic2 the images have been pregenerated for all selectable point sizes. This will leave some of the characters that you find in the graphical parent/child lists not rendered because they're either old Japanese kanji, old Chinese characters, or 'not actually a kanji but found in unicode' glyphs.