• Accessibility
• Optimization
  • On the wire
  • In the browser
• Cross-Domain Ajax

• It's possible to make accessible Ajax UI's
• It's not easy
• But it's getting easier

• Focus
• Feedback
• "What Is It?"

• Large-text modes
• High-contrast mode
• "Large-target" modes
• Colorblindness
• Other Section 508

• Clean HTML helps
• WAI role and state information
• Tabindex for keyboard navigation
• Poor communication with assistive technologies
• Slow a11y tech upgrades
• W3C WCAG isn't helping anything

• Defines richer set of what something "is"
• Must live in XHTML 2 namespace
• Needs to be set at runtime
• Calling focus() almost well supported
• Setting up keyboard accellerators is difficult
• Dijit Widgets fully a11y hinted

Ajax a11y Is Hindered By Lack Of "HTML Subclassing"

Optimization

• Bandwidth
• Latency
• Parallel or Serial?

• Safari 3 Web Inspector
• Firebug
• Ethereal
• Server logs

• Cache
• Make it smaller
• Request fewer resources
• Parallelize
• Delay loading
• Host closer to endpoint

• Client side
  • Expect 50% cache miss rates at scale
  • Last-Modified, Cache-Control, ETags, If-Modified-Since
  • IE is fickle!
  • Cal Henderson's "Serving JavaScript Fast" article
• Server side
  • Squid
  • memcached
  • mod_cache and physical partitions
  • Database tuning

• gzip encoding (mod_deflate)
• White space and comment removal (then cache!)
• Dead code stripping

• Concat smaller JS into larger "common" files
• CSS background image "trick"
• Exotic MIME games

• JS files are loaded serially
• 2 connections per domain!
• Host static resource "off domain"
• Sub-domains count
• CDN's help

• Load code in response to user actions
• Requires careful development practices
• Or a package system
• Dojo provides such a system

• CDN's
• Exotic form of caching
• AOL hosts Dojo in their CDN for all to use

• Tools much less mature
• Firebug profiling
• Custom test harnesses
• Hard-won experience with various rendering engines

• innerHTML fast vs. DOM
• JS iteration is slow
• JS regular expressions are slow
• JS function calls are fast but not free
• IE GC "wall" (for now)
• "First visit" hit

• "Closures cause memory leakage"
• "DOM iteration is slow"
• "External style sheets are faster"
• "Objects are cheap"
• "Array joins are faster than string addition"

• Never guess
• Starting from the top and work down to slow components
• Keep a log
• Know when to stop
• If it's not what your clients are using, it's not what your clients are using
• Leakage !== Peak Memory Usage Increases

• Local data can be more interesting when given context
• Mashups do this in an ad-hoc way
• Better understanding of techniques will drive adoption

• Pioneered by James Burke of AOL (Dojo committer)
• Requires explicit cooperation of 3rd-party domain
• Can return HTML document content
• Few worries about malicious content or cookie leakage
• May be slow

• Proposal from Bob Ippolito
• Requires explicit cooperation of server
• Very fast, can return content of arbitrary type and size
• Variant already in use by Yahoo
• Potentially unsafe, executes remote code in page context

X-Z of Y results

• IBM SMash
• Microsoft "SubSpace"
• <module> tag proposal
• Whatever Gears does

• http://flickr.com/photo_zoom.gne?id=184612846&size=o
• http://flickr.com/photos/myradphotos/3111332/