How to Nullify CSS Property

How can I nullify css property?

You have to reset each individual property back to its default value. It's not great, but it's the only way, given the information you've given us.

In your example, you would do:

.c1 {
    height: auto;
}

You should search for each property here:

https://developer.mozilla.org/en-US/docs/Web/CSS/Reference

For example, height:

Initial value : auto

Another example, max-height:

Initial value : none

In 2017, there is now another way, the unset keyword:

.c1 {
    height: unset;
}

Some documentation: https://developer.mozilla.org/en-US/docs/Web/CSS/unset

The unset CSS keyword is the combination of the initial and inherit
keywords. Like these two other CSS-wide keywords, it can be applied to
any CSS property, including the CSS shorthand all. This keyword resets
the property to its inherited value if it inherits from its parent or
to its initial value if not. In other words, it behaves like the
inherit keyword in the first case and like the initial keyword in the
second case.

Browser support is good: http://caniuse.com/css-unset-value

Reset/remove CSS styles for element only

The CSS3 keyword initial sets the CSS3 property to the initial value as defined in the spec. The initial keyword has broad browser support except for the IE and Opera Mini families.

Since IE's lack of support may cause issue here are some of the ways you can reset some CSS properties to their initial values:

.reset-this {
    animation : none;
    animation-delay : 0;
    animation-direction : normal;
    animation-duration : 0;
    animation-fill-mode : none;
    animation-iteration-count : 1;
    animation-name : none;
    animation-play-state : running;
    animation-timing-function : ease;
    backface-visibility : visible;
    background : 0;
    background-attachment : scroll;
    background-clip : border-box;
    background-color : transparent;
    background-image : none;
    background-origin : padding-box;
    background-position : 0 0;
    background-position-x : 0;
    background-position-y : 0;
    background-repeat : repeat;
    background-size : auto auto;
    border : 0;
    border-style : none;
    border-width : medium;
    border-color : inherit;
    border-bottom : 0;
    border-bottom-color : inherit;
    border-bottom-left-radius : 0;
    border-bottom-right-radius : 0;
    border-bottom-style : none;
    border-bottom-width : medium;
    border-collapse : separate;
    border-image : none;
    border-left : 0;
    border-left-color : inherit;
    border-left-style : none;
    border-left-width : medium;
    border-radius : 0;
    border-right : 0;
    border-right-color : inherit;
    border-right-style : none;
    border-right-width : medium;
    border-spacing : 0;
    border-top : 0;
    border-top-color : inherit;
    border-top-left-radius : 0;
    border-top-right-radius : 0;
    border-top-style : none;
    border-top-width : medium;
    bottom : auto;
    box-shadow : none;
    box-sizing : content-box;
    caption-side : top;
    clear : none;
    clip : auto;
    color : inherit;
    columns : auto;
    column-count : auto;
    column-fill : balance;
    column-gap : normal;
    column-rule : medium none currentColor;
    column-rule-color : currentColor;
    column-rule-style : none;
    column-rule-width : none;
    column-span : 1;
    column-width : auto;
    content : normal;
    counter-increment : none;
    counter-reset : none;
    cursor : auto;
    direction : ltr;
    display : inline;
    empty-cells : show;
    float : none;
    font : normal;
    font-family : inherit;
    font-size : medium;
    font-style : normal;
    font-variant : normal;
    font-weight : normal;
    height : auto;
    hyphens : none;
    left : auto;
    letter-spacing : normal;
    line-height : normal;
    list-style : none;
    list-style-image : none;
    list-style-position : outside;
    list-style-type : disc;
    margin : 0;
    margin-bottom : 0;
    margin-left : 0;
    margin-right : 0;
    margin-top : 0;
    max-height : none;
    max-width : none;
    min-height : 0;
    min-width : 0;
    opacity : 1;
    orphans : 0;
    outline : 0;
    outline-color : invert;
    outline-style : none;
    outline-width : medium;
    overflow : visible;
    overflow-x : visible;
    overflow-y : visible;
    padding : 0;
    padding-bottom : 0;
    padding-left : 0;
    padding-right : 0;
    padding-top : 0;
    page-break-after : auto;
    page-break-before : auto;
    page-break-inside : auto;
    perspective : none;
    perspective-origin : 50% 50%;
    position : static;
    /* May need to alter quotes for different locales (e.g fr) */
    quotes : '\201C' '\201D' '\2018' '\2019';
    right : auto;
    tab-size : 8;
    table-layout : auto;
    text-align : inherit;
    text-align-last : auto;
    text-decoration : none;
    text-decoration-color : inherit;
    text-decoration-line : none;
    text-decoration-style : solid;
    text-indent : 0;
    text-shadow : none;
    text-transform : none;
    top : auto;
    transform : none;
    transform-style : flat;
    transition : none;
    transition-delay : 0s;
    transition-duration : 0s;
    transition-property : none;
    transition-timing-function : ease;
    unicode-bidi : normal;
    vertical-align : baseline;
    visibility : visible;
    white-space : normal;
    widows : 0;
    width : auto;
    word-spacing : normal;
    z-index : auto;
    /* basic modern patch */
    all: initial;
    all: unset;
}

/* basic modern patch */

#reset-this-root {
    all: initial;
    * {
        all: unset;
    }
}

Relevent github repo with a december 2017 more exaustive list
Related
Related from MDN
Related W3C specs

As mentioned in a comment by @user566245 :

this is correct in principle, but individual mileage may vary. For
example certain elements like textarea by default have a border,
applying this reset will render those textarea's border less.

JAVASCRIPT ?

Nobody thought about other than css to reset css? Yes?

There is that snip fully relevant : https://stackoverflow.com/a/14791113/845310

getElementsByTagName("*") will return all elements from DOM. Then you
may set styles for each element in the collection:

answered Feb 9 '13 at 20:15 by VisioN

var allElements = document.getElementsByTagName("*");
for (var i = 0, len = allElements.length; i < len; i++) {
    var element = allElements[i];
    // element.style.border = ...
}

With all this said; i don't think a css reset is something feasable unless we end up with only one web browser .. if the 'default' is set by browser in the end.

For comparison, here is Firefox 40.0 values list for a
<blockquote style="all: unset;font-style: oblique"> where font-style: oblique triggers DOM operation.

align-content: unset;
align-items: unset;
align-self: unset;
animation: unset;
appearance: unset;
backface-visibility: unset;
background-blend-mode: unset;
background: unset;
binding: unset;
block-size: unset;
border-block-end: unset;
border-block-start: unset;
border-collapse: unset;
border-inline-end: unset;
border-inline-start: unset;
border-radius: unset;
border-spacing: unset;
border: unset;
bottom: unset;
box-align: unset;
box-decoration-break: unset;
box-direction: unset;
box-flex: unset;
box-ordinal-group: unset;
box-orient: unset;
box-pack: unset;
box-shadow: unset;
box-sizing: unset;
caption-side: unset;
clear: unset;
clip-path: unset;
clip-rule: unset;
clip: unset;
color-adjust: unset;
color-interpolation-filters: unset;
color-interpolation: unset;
color: unset;
column-fill: unset;
column-gap: unset;
column-rule: unset;
columns: unset;
content: unset;
control-character-visibility: unset;
counter-increment: unset;
counter-reset: unset;
cursor: unset;
display: unset;
dominant-baseline: unset;
empty-cells: unset;
fill-opacity: unset;
fill-rule: unset;
fill: unset;
filter: unset;
flex-flow: unset;
flex: unset;
float-edge: unset;
float: unset;
flood-color: unset;
flood-opacity: unset;
font-family: unset;
font-feature-settings: unset;
font-kerning: unset;
font-language-override: unset;
font-size-adjust: unset;
font-size: unset;
font-stretch: unset;
font-style: oblique;
font-synthesis: unset;
font-variant: unset;
font-weight: unset;
font: ;
force-broken-image-icon: unset;
height: unset;
hyphens: unset;
image-orientation: unset;
image-region: unset;
image-rendering: unset;
ime-mode: unset;
inline-size: unset;
isolation: unset;
justify-content: unset;
justify-items: unset;
justify-self: unset;
left: unset;
letter-spacing: unset;
lighting-color: unset;
line-height: unset;
list-style: unset;
margin-block-end: unset;
margin-block-start: unset;
margin-inline-end: unset;
margin-inline-start: unset;
margin: unset;
marker-offset: unset;
marker: unset;
mask-type: unset;
mask: unset;
max-block-size: unset;
max-height: unset;
max-inline-size: unset;
max-width: unset;
min-block-size: unset;
min-height: unset;
min-inline-size: unset;
min-width: unset;
mix-blend-mode: unset;
object-fit: unset;
object-position: unset;
offset-block-end: unset;
offset-block-start: unset;
offset-inline-end: unset;
offset-inline-start: unset;
opacity: unset;
order: unset;
orient: unset;
outline-offset: unset;
outline-radius: unset;
outline: unset;
overflow: unset;
padding-block-end: unset;
padding-block-start: unset;
padding-inline-end: unset;
padding-inline-start: unset;
padding: unset;
page-break-after: unset;
page-break-before: unset;
page-break-inside: unset;
paint-order: unset;
perspective-origin: unset;
perspective: unset;
pointer-events: unset;
position: unset;
quotes: unset;
resize: unset;
right: unset;
ruby-align: unset;
ruby-position: unset;
scroll-behavior: unset;
scroll-snap-coordinate: unset;
scroll-snap-destination: unset;
scroll-snap-points-x: unset;
scroll-snap-points-y: unset;
scroll-snap-type: unset;
shape-rendering: unset;
stack-sizing: unset;
stop-color: unset;
stop-opacity: unset;
stroke-dasharray: unset;
stroke-dashoffset: unset;
stroke-linecap: unset;
stroke-linejoin: unset;
stroke-miterlimit: unset;
stroke-opacity: unset;
stroke-width: unset;
stroke: unset;
tab-size: unset;
table-layout: unset;
text-align-last: unset;
text-align: unset;
text-anchor: unset;
text-combine-upright: unset;
text-decoration: unset;
text-emphasis-position: unset;
text-emphasis: unset;
text-indent: unset;
text-orientation: unset;
text-overflow: unset;
text-rendering: unset;
text-shadow: unset;
text-size-adjust: unset;
text-transform: unset;
top: unset;
transform-origin: unset;
transform-style: unset;
transform: unset;
transition: unset;
user-focus: unset;
user-input: unset;
user-modify: unset;
user-select: unset;
vector-effect: unset;
vertical-align: unset;
visibility: unset;
white-space: unset;
width: unset;
will-change: unset;
window-dragging: unset;
word-break: unset;
word-spacing: unset;
word-wrap: unset;
writing-mode: unset;
z-index: unset;

How Do I Cancel Out A CSS Property?

You can use color: inherit to have the color use the value from its ancestors. color is odd in that it has different default values depending on context. A link, for example, will typically default to blue, while text will default to black.

If you need to override the existing style, don't use a more specific selector. Raising the specificity means that you'll just have to use more selectors the next time you want to override it.

Instead, take advantage of the cascade by using a selector with identical specificity and make the override happen after the original style:

/* older style in some library */
.foo .bar .baz {
    color: blue;
}

...in an overriding CSS file...

.foo .bar .baz {
    color: green;
}

Remove CSS property completely

You can remove the original stylesheet. Just assign it an id and use jQuery.remove(...).

The alternate solution is to alter the first stylesheet to use some kind of namespace⁺, for example:

/* these are the rules that you want to be removed */
.stylesheet1       { }
.stylesheet1 h1    { }
.stylesheet1 p     { }
.stylesheet1 a     { }
.stylesheet1 input { }
/* these rules can co-exist with the next stylesheet */
nav                { }
article            { }
aside              { }
section            { }

Inside your HTML add the stylesheet1 class to body. When you load the other CSS file (presumably via JavaScript) then you remove this class. All namespaced rules will become ineffective.

^* CSS preprocessors e.g. SASS and LESS make it easier for you to manage these rules.

Remove CSS Property by Javascript

Relevant : How can you remove an important CSS property?

To quote user Dagg Nabbit from the link:

The reason you can't remove the property is because it's a shorthand property

When you set it, other properties actually get added, but no "background" property, so there's no "background" property to remove.

In this case, you can unset it like this:

elem.style.removeProperty('background-color');

In general, you'd need to unset every "long-hand" property represented by the shorthand property.

You could also do this to overwrite it:

elem.style.setProperty('background', 'inherit', 'important');

Or you could nuke the entire inline style for the element like this:

elem.style.cssText = '';

how to remove css property using javascript?

You have two options:

OPTION 1:

You can use removeProperty method. It will remove a style from an element.

el.style.removeProperty('zoom');

OPTION 2:

You can set it to the default value:

el.style.zoom = "";

The effective zoom will now be whatever follows from the definitions set in the stylesheets (through link and style tags). So this syntax will only modify the local style of this element.