References

Characters reference, Symbols reference
ASCII and ISO Latin-1 characters are shown along with their corresponding decimal and hexadecimal values and HTML codes. Symbols, mathematical symbols and greek letters.
Colours in HTML, Colour nuances
These pages show the standard named colours, the 216-colour palette and colour nuances. The standard named colours are recognized by all browsers and the 216-colour palette works on most platform without dithering.
Colour names
There are more colour names than the standard 16 names. Here you can find an extensive non-standard colour names list, but certain browsers might not recognize them.
JDE quick reference
Quick reference cards for JDEE commands.
Comparison of different SQL implementations
A very useful document by Troels Arvin, that compares the differences in SQL implementation between major RDBMS products.