Create anchors using the Anchor macro. The following macro:
== Section One[[Anchor one]] == ... blah blah[[Anchor my-anchor]] blah
inserts the following HTML into your page:
<h2>Section One<a name="one"></a></h2> ... blah blah<a name="my-anchor"></a> blah
Only alphanumeric characters and dashes are permitted in anchors. Underscores (correct me if I'm wrong -- (SM)?) are technically not allowed by the XHTML specification.
From the [HTML 4 specs]: ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"), colons (":"), and periods ("."). Note also that in XHTML, the name attribute is deprecated in favor of the id attribute (for compatibility it is recommended that you use both: e.g. <a name="foo" id="foo"></a> [1]. (XML restricts the value of an id to be of type [Name], but, so far as I can tell, that's a superset of the values allowed by the HTML 4 specs quoted above.)
To link to anchors, add a '#anchor-name' to your page link, as follows:
SandBox#one ((SandBox#one)) ((SandBox|sand-box, first section#one))
which display as: