min-width , max-width

I have a question about the below style applied to an image

width: 80%;
max-width: 1000px;
min-width: 260px;

is the min and max-width not enough to make the image responsive ?? why the 80% ? to control what ?

IE9 does not work with max-width and min-width

I am wanting to put a form 100% on screen, but with restrictions for a minimum and maximum width, ie, I want you 100% of the width of the screen, but at most 1250 and at least 950.

Code works in chrome and ff:

<body style="padding:0px;margin:0px;">
<div style="max-width:1250;min-width:950;width:100%;background-color:#F00;">
<div style="width:50%;background-color:#0F0;">
<input style="width:50%;">

Thanks and sorry for my poor english.

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