Visit http://en.wikipedia.org/w/api.php?action=parse&page=USB&prop=sections
Some of the entries have crazy html in them, such as (see the part that says "line":
{
"toclevel": 3,
"level": "4",
"line": "<span></span><span></span><span></span><span></span><span></span>Prereleases",
"number": "2.1.1",
"index": "4",
"fromtitle": "USB",
"byteoffset": 13726,
"anchor": "Prereleases"
},
This is due to the markup for that section being
```
==== {{anchor|0.7|0.8|0.9|0.99|1.0RC}}Prereleases ====
```
which translates to
```
==== <span id="0.7"></span><span id="0.8"></span><span id="0.9"></span><span id="0.99"></span><span id="1.0RC"></span>Prereleases ====
```
and when the parser strips attributes but leaves the `<span>` tags it gives the result shown. Tidy (probably) fixes it on WMF sites, but why generate it in the first place?