在 TechCrunch 上看到的「Gmail, We Need To Talk」這篇裡提到 Gmail 的問題，尤其是 CSS 這塊：
Each Gmail client renders email differently. You may not be aware of this, but each Gmail client has its own set of frustrating quirks. Having to deal with each version of Gmail makes creating email a nail-biting chore:
- Gmail.com Webmail. Supports <style> but does not support ids and classes.
- Gmail Webmail for Business. Does not support <style>.
- Gmail App for iOS. Randomly increases font sizes by 50 percent (no <style>).
- Gmail App for Android. Randomly ignores container widths (no <style>).
- Gmail App for Android (for non Gmail.com addresses). Does not support background images in addition to ignoring container widths (no <style>).
- Inbox by Gmail for Android. Randomly ignores container widths but does so differently than Gmail App for Android (no <style>).
- Inbox by Gmail for iOS. Does not support <style> but seems to not suffer from as many quirks as other Gmail mobile apps.