Found the following HTML validation problems:
Euler.html:19:1 (Euler.Rd:9): Warning: <h2> attribute "function'" lacks value
Euler.html:19:1 (Euler.Rd:9): Warning: <h2> attribute "id" has invalid value "17. Euler"
Euler.html:19:1 (Euler.Rd:9): Warning: <h2> proprietary attribute "s"
Euler.html:19:1 (Euler.Rd:9): Warning: <h2> proprietary attribute "phi"
Fibonacci.html:19:1 (Fibonacci.Rd:16): Warning: <h2> attribute "id" has invalid value "23. Fibonacci numbers"
Jacobi.html:19:1 (Jacobi.Rd:9): Warning: <h2> attribute "id" has invalid value "16. Jacobi Symbol"
Legendre.html:19:1 (Legendre.Rd:9): Warning: <h2> attribute "formula'" lacks value
Legendre.html:19:1 (Legendre.Rd:9): Warning: <h2> attribute "id" has invalid value "13. Legrendre"
Legendre.html:19:1 (Legendre.Rd:9): Warning: <h2> proprietary attribute "s"
Pi.html:19:1 (Pi.Rd:9): Warning: <h2> attribute "id" has invalid value "21. Pi function"
arithmeticlogic.html:19:1 (arithmeticlogic.Rd:18): Warning: <h2> attribute "id" has invalid value "02. Arithmetic and logic"
binom.html:19:1 (binom.Rd:9): Warning: <h2> attribute "id" has invalid value "06. Binomial coefficients"
count1bits.html:19:1 (count1bits.Rd:9): Warning: <h2> attribute "id" has invalid value "25. Counting 1 bits"
divisor.html:19:1 (divisor.Rd:9): Warning: <h2> attribute "id" has invalid value "14. Finding a random divisor"
divp2.html:19:1 (divp2.Rd:9): Warning: <h2> attribute "id" has invalid value "05. Efficent division by a power of 2"
exteuclid.html:19:1 (exteuclid.Rd:9): Warning: <h2> attribute "id" has invalid value "11. Extended Euclidean algorithm"
factorial.html:19:1 (factorial.Rd:9): Warning: <h2> attribute "id" has invalid value "07. Factorial"
factors.html:19:1 (factors.Rd:9): Warning: <h2> attribute "id" has invalid value "15. Factorization"
gcd.html:19:1 (gcd.Rd:9): Warning: <h2> attribute "id" has invalid value "09. Greatest common divisor"
lcmul.html:19:1 (lcmul.Rd:9): Warning: <h2> attribute "id" has invalid value "10. Least common multiple"
logarithms.html:19:1 (logarithms.Rd:19): Warning: <h2> attribute "id" has invalid value "04. Logarithms"
modarithmeticop.html:19:1 (modarithmeticop.Rd:29): Warning: <h2> attribute "id" has invalid value "08. Modular-arithmetic"
nextprime.html:19:1 (nextprime.Rd:9): Warning: <h2> attribute "id" has invalid value "20. Next prime number"
perfectpow.html:19:1 (perfectpow.Rd:13): Warning: <h2> attribute "id" has invalid value "12. Perfect power"
primality.html:19:1 (primality.Rd:18): Warning: <h2> attribute "id" has invalid value "18. Probabilistic primality tests"
primes.html:19:1 (primes.Rd:9): Warning: <h2> attribute "id" has invalid value "19. Finding all primes"
primescount.html:19:1 (primescount.Rd:9): Warning: <h2> attribute "id" has invalid value "22. Counting the number of primes"
random.html:19:1 (random.Rd:22): Warning: <h2> attribute "id" has invalid value "24. Random generators"
roots.html:19:1 (roots.Rd:18): Warning: <h2> attribute "id" has invalid value "03. Roots"
vli.html:19:1 (vli.Rd:17): Warning: <h2> attribute "id" has invalid value "01. Basics"