Why do browsers use different css rules when they work and are defined almost identically? -

i've used lot of css , how use it. understand why have put properties in order different browser same thing. question is: why don't browsers implement of more common properties? example:

i need text not selectable, add this:

-webkit-touch-callout: none; -webkit-user-select: none; -khtml-user-select: none; -moz-user-select: none; -ms-user-select: none; user-select: none; 

nearly of them user-select , last one, 1 seems should supported on multiple browsers, not supported @ all.

does know why @ least browsers don't start migrating universal standard? if has same thing, perhaps browsers can put effort fixing this?

i understand if mozilla got rid of -moz-user-select, pages break, doesn't mean can't add user-select more pages work.

any ideas?

browser prefixed properties meant used beta/trial/demonstration/experimental/{inser more adjectives here} , not implemented or part of property standard documentation isn't finished/approved/done.

when feature usable, it's dropped prefix , used 'standard'.

you can see how experimental how have declare ways gradient backgrounds proposed on years, 'standard' version last:

background: #1e5799; /* old browsers */ filter: progid:dximagetransform.microsoft.gradient( startcolorstr='#1e5799', endcolorstr='#7db9e8',gradienttype=0 ); /* ie6-8 */ background: -moz-linear-gradient(top,  #1e5799 0%, #2989d8 50%, #207cca 51%, #7db9e8 100%); /* ff3.6+ */ background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#1e5799), color-stop(50%,#2989d8), color-stop(51%,#207cca), color-stop(100%,#7db9e8)); /* chrome,safari4+ */ background: -webkit-linear-gradient(top,  #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* chrome10+,safari5.1+ */ background: -o-linear-gradient(top,  #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* opera 11.10+ */ background: -ms-linear-gradient(top,  #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* ie10+ */ background: linear-gradient(to bottom,  #1e5799 0%,#2989d8 50%,#207cca 51%,#7db9e8 100%); /* w3c */ 

from http://www.colorzilla.com/gradient-editor/

refer comments on above code each browser version.

also, read: http://davidwalsh.name/vendor-prefixes quote:

why vendor prefixes?

there few reasons browser vendors use prefixes:

• to implement proprietary css properties have no working standard , may never become standard
• to provide implementations of standard properties
• to provide alternate syntax standard
• other reasons may apply these main reasons.