Latency is a major concern for web rendering engines
like those in Chrome, Safari, and Firefox.
These engines reduce latency by using
an \emph{incremental layout algorithm}
to redraw the page when
the user interacts with it.
In such an algorithm,
elements that change frame-to-frame are marked dirty, and
only those elements are processed
to draw the next frame,
dramatically reducing latency.
However, the standard incremental layout algorithm
must search the page for dirty elements,
accessing auxiliary elements in the process.
These auxiliary elements
add cache misses and stalled cycles,
and are responsible for a sizable fraction
of all layout latency.

We introduce a new, faster incremental layout algorithm
called Spineless Traversal.
Spineless Traversal
uses a cache-friendlier priority queue algorithm
that avoids accessing auxiliary nodes
and thus reduces cache traffic and stalls.
This leads to dramatic speedups
on the most latency-critical interactions
such as hovering, typing, and animation.
Moreover, thanks to numerous low-level optimizations,
Spineless Traversal is competitive
across the whole spectrum of incremental layout workloads.
Spineless Traversal is faster than the standard approach
on $83.0%\xspace$ of $2216~$benchmarks,
with a mean speedup of $\ensuremath{1.80\times}\xspace$
concentrated in the most latency-critical interactions.