To make sure that your code will keep working as expected in the future, do not use obsolete properties:

Noncompliant Code Example

.mybox {
  azimuth: 30deg; /* Noncompliant */
  appearance: normal; /* Noncompliant */
}

Obsolete Properties

alignment-adjust appearance azimuth  #2  #3
behavior binding border-end
border-end-color border-end-style border-end-width
border-start border-start-color border-start-style
border-start-width box-align box-direction
box-flex box-flex-group box-lines
box-ordinal-group box-orient box-pack
drop-initial-after-adjust drop-initial-after-align drop-initial-before-adjust
drop-initial-before-align drop-initial-size drop-initial-value
elevation  #2 fit fit-position
glyph-orientation-horizontal  #2 glyph-orientation-vertical  #2  #3 grid-cell-stacking
grid-column-align grid-column-sizing grid-column-span
grid-columns grid-flow grid-layer
grid-row-align grid-row-sizing grid-row-span
grid-rows hyphenate-after hyphenate-before
hyphenate-lines hyphenate-resource ime-mode  #2
line-stacking line-stacking-ruby line-stacking-shift
line-stacking-strategy margin-end margin-start
marquee marquee-dir marquee-direction
marquee-increment marquee-loop marquee-play-count
marquee-repetition marquee-speed marquee-style
move-to nav-index padding-end
padding-start page-policy phonemes
pitch pitch-range play-during
presentation-level progress-appearance punctuation-trim
richness rotation rotation-point
ruby-overhang ruby-span scollbar-arrow-color
scollbar-base-color scollbar-dark-shadow-color scollbar3dlight-color
scrollbar-face-color speak-header speak-numeral
speak-punctuation speech-rate stress
target target-name target-new
target-position text-kashida-space  #2 text-outline
text-stroke user-modify view-state
volume  #2 white-space-collapse word-wrap