Transition of background-color - css

Question

I'm trying to make a transition effect with background-color when hovering menu items, but it does not work. Here is my CSS code:
#content #nav a:hover {
color: black;
background-color: #AD310B;
/* Firefox */
-moz-transition: all 1s ease-in;
/* WebKit */
-webkit-transition: all 1s ease-in;
/* Opera */
-o-transition: all 1s ease-in;
/* Standard */
transition: all 1s ease-in;
}
The #nav div is a menu ul list of items.

Answer 1

As far as I know, transitions currently work in Safari, Chrome, Firefox, Opera and Internet Explorer 10+.
This should produce a fade effect for you in these browsers:
a {
background-color: #FF0;
}
a:hover {
background-color: #AD310B;
-webkit-transition: background-color 1000ms linear;
-ms-transition: background-color 1000ms linear;
transition: background-color 1000ms linear;
}
<a>Navigation Link</a>
Note: As pointed out by Gerald in the comments, if you put the transition on the a, instead of on a:hover it will fade back to the original color when your mouse moves away from the link.
This might come in handy, too: CSS Fundamentals: CSS 3 Transitions
ps.
As #gak comment below
You can also put in the transitions into content #nav a for fading back to the original when the user moves the mouse away from the link

Answer 2

To me, it is better to put the transition codes with the original/minimum selectors than with the :hover or any other additional selectors:
#content #nav a {
background-color: #FF0;
-webkit-transition: background-color 1000ms linear;
-moz-transition: background-color 1000ms linear;
-o-transition: background-color 1000ms linear;
-ms-transition: background-color 1000ms linear;
transition: background-color 1000ms linear;
}
#content #nav a:hover {
background-color: #AD310B;
}
<div id="content">
<div id="nav">
Link 1
</div>
</div>

Answer 3

Another way of accomplishing this is using animation which provides more control.
/* declaring the states of the animation to transition through */
/* optionally add other properties that will change here, or new states (50% etc) */
#keyframes onHoverAnimation {
0% {
background-color: #FF0;
}
100% {
background-color: #AD310B;
}
}
#content #nav a {
background-color: #FF0;
/* only animation-duration here is required, rest are optional (also animation-name but it will be set on hover)*/
animation-duration: 1s; /* same as transition duration */
animation-timing-function: linear; /* kind of same as transition timing */
animation-delay: 0ms; /* same as transition delay */
animation-iteration-count: 1; /* set to 2 to make it run twice, or Infinite to run forever!*/
animation-direction: normal; /* can be set to "alternate" to run animation, then run it backwards.*/
animation-fill-mode: none; /* can be used to retain keyframe styling after animation, with "forwards" */
animation-play-state: running; /* can be set dynamically to pause mid animation*/
}
#content #nav a:hover {
/* animation wont run unless the element is given the name of the animation. This is set on hover */
animation-name: onHoverAnimation;
}

Answer 4

You can simply set transition to a tag styles and change background in hover
a {
background-color: #FF0;
transition: background-color 300ms linear;
-webkit-transition: background-color 300ms linear;
-ms-transition: background-color 300ms linear;
-o-transition: background-color 300ms linear;
-ms-transition: background-color 300ms linear;
}
a:hover {
background-color: #AD310B;
}
<a>Link</a>