On 2016-12-05 Mon 00:25 GMT-0800, Katsumi Yamaoka <yamaoka@jpl.org> wrote:

> On Sun, 04 Dec 2016 12:01:57 -0800, Hong Xu wrote:
>> That's exactly what I meant: Every time it is referred, it is bound to
>> nil by a let.
>
> `shr-tag-a' binds `shr-start' to nil, runs `shr-generic' that
> sets non-nil value to `shr-start' in the following way, and
> refers to `shr-start'.
>
> `shr-generic' runs `shr-descend'
> `shr-descend' runs `shr-tag-img'
> `shr-tag-img' sets non-nil value to `shr-start'
>
> ;-)

Such a complicated story! Thank you for pointing it out!