How to cancel left or right rules with an !important tag?

Tags: html,css

Problem :

I need to cancel a left rule in a CSS file and replace it with margin-left:

.aClass {
    left: 5px;
} 

Rule to override:

.aClass {
    left: none !important;
    margin-left: 5px;
}

but left: none doesn't seem to do nothing and left: 0 is repositioning the layer. So how to cancel the left rule? I shouldn't override the original rule, as it is a part of a plugin and it could be updated overriding the existing file.

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Solution :

Use left: auto !important; instead of left: none !important;