The upper figure illustrates the convergence of the frequency (\hat{p}) to the probability $p$.
If the frequency $\hat{p}$ is not near 1 or 0 and then sample size $N$ is sufficiently large then the $1-\alpha$ confidence interval is
$$\hat{p} \pm z_{1-\alpha/2} \sqrt{\frac{\hat{p}(1-\hat{p})}{N}} $$ Green horizonal lines show the confidence interval for $\alpha=0.01$.
The lower figure shows that for $p=0.5$ the number of heads does not converge to the number of tails, or equivalently that the difference between those two numbers does not converge to zero.
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.