Normalize.css can initialize CSS, different browsers can unify the initial style

/*! Normalize.css v7.0.0 | MIT License | Github.com/necolas/normalize.css *//* Document ================================================================== ======== *//** * 1. Correct The line height is browsers. * 2. Prevent adjustments of font size after orientation changes in * IE on Windows Phone and in IOS.  */html {line-height:1.15;  /* 1 */-ms-text-size-adjust:100%; /* 2 */-webkit-text-size-adjust:100%/* 2 */}/* Sections =========================================================== =============== *//** * Remove the margin in all browsers (opinionated). */body {margin:0;} /** * Add The correct display in IE 9-. */article,aside,footer,header,nav,section {display:block;} /** * Correct the font size and margin on ' H1 ' elements within ' sections ' and * ' article ' contexts in Chrome, Firefox, and Safari.  */h1 {font-size:2em; Margin:0.67em 0;} /* Grouping content ========================================================================== *//** * Add the correctDisplay in IE 9-. * 1. ADD the correct display in IE. */figcaption,figure,main {/* 1 */display:block;} /** * Add the correct margin in IE 8. */figure {margin:1em 40px;} /** * 1. Add the correct box sizing in Firefox. * 2. Show the overflow in Edge and IE.  */hr {box-sizing:content-box;  /* 1 */height:0; /* 1 */overflow:visible/* 2 */}/** * 1. Correct the inheritance and scaling of font size in all browsers. * 2. Correct the odd ' em ' font sizing in all browsers.  */pre {font-family:monospace, monospace; /* 1 */font-size:1em/* 2 */}/* text-level semantics =============================================================== =========== *//** * 1. Remove the gray background on active links in IE 10. * 2. Remove gaps in links underline in IOS 8+ and Safari 8+.  */a {background-color:transparent; /* 1 */-webkit-text-decoration-skip:objects/* 2 */}/** * 1. Remove the bottom border in Chrome 57-and Firefox 39-. * 2. Add the correct text decoration in Chrome, Edge, IE, Opera, and Safari.  */abbr[title] {border-bottom:none;  /* 1 */text-decoration:underline; /* 2 */text-decoration:underline dotted/* 2 */}/** * Prevent the duplicate application of ' bolder ' by the next rule I N Safari 6. */b,strong {Font-weight:inherit;} /** * Add The correct font weight in Chrome, Edge, and Safari. */b,strong {font-weight:bolder;} /** * 1. Correct the inheritance and scaling of font size in all browsers. * 2. Correct the odd ' em ' font sizing in all browsers.  */code,kbd,samp {font-family:monospace, monospace; /* 1 */font-size:1em/* 2 */}/** * Add the correct font style in Android 4.3-. */DFN {font-style:italic;} /** * Add the correct background and color in IE 9-.  */mark {background-color: #ff0; Color: #000;} /** * Add The correct font size in all browsers. */small {font-size:80%;} /** * Prevent ' Sub ' and ' SUP ' elements from affecting the line height in * all browsers.  */sub,sup {font-size:75%;  line-height:0;  position:relative;Vertical-align:baseline;} Sub {bottom: -0.25em;} sup {top: -0.5em;} /* Embedded content ========================================================================== *//** * Add the correct Display in IE 9-. */audio,video {display:inline-block;} /** * Add The correct display in IOS 4-7.  */audio:not ([controls]) {Display:none; height:0;} /** * Remove The border on images inside links in IE 10-. */img {border-style:none;} /** * Hide the overflow in IE. */svg:not (: root) {Overflow:hidden;} /* Forms ========================================================================== *//** * 1. The change of the font styles in all browsers (opinionated). * 2. Remove the margin in Firefox and Safari.  */button,input,optgroup,select,textarea {font-family:sans-serif;  /* 1 */font-size:100%;  /* 1 */line-height:1.15; /* 1 */margin:0/* 2 */}/** * Show the overflow in IE. * 1. Show the overflow in Edge. */button,input {/* 1 */overflow:visible;} /** * Remove The inheritance of text traNsform in Edge, Firefox, and IE. * 1. Remove the inheritance of text transform in Firefox. */button,select {/* 1 */text-transform:none;} /** * 1. Prevent a WebKit bug where (2) destroys native ' audio ' and ' video ' * Controls in Android 4. * 2. Correct the inability to style clickable types in IOS and Safari.  */button,html [type= "button"],[type= "reset"],[type= "submit"] {-webkit-appearance:button/* 2 */}/** * Remove the inner Border and padding in Firefox. */button::-moz-focus-inner,[type= "button"]::-moz-focus-inner,[type= "reset"]::-moz-focus-inner,[type= "Submit"]:  :-moz-focus-inner {border-style:none; padding:0;} /** * Restore The Focus styles unset by the previous rule. */button:-moz-focusring,[type= "button"]:-moz-focusring,[type= "reset"]:-moz-focusring,[type= "Submit"]:- moz-focusring {outline:1px dotted buttontext;} /** * Correct the padding in Firefox. */fieldset {padding:0.35em 0.75em 0.625em;} /** * 1. Correct the text wrapping in Edge and IE. * 2. Correct the ColoR inheritance from ' FieldSet ' elements in IE. * 3. Remove The padding so developers is not a caught out when they zero out * ' fieldset ' elements on all browsers.  */legend {box-sizing:border-box;  /* 1 */color:inherit;  /* 2 */display:table;  /* 1 */max-width:100%;  /* 1 */padding:0; /* 3 */white-space:normal/* 1 */}/** * 1. ADD the correct display in IE 9-. * 2. Add the correct vertical alignment in Chrome, Firefox, and Opera.  */progress {display:inline-block; /* 1 */vertical-align:baseline/* 2 */}/** * Remove The default vertical scrollbar in IE. */textarea {Overflow:auto;} /** * 1. Add the correct box sizing in IE 10-. * 2. Remove the padding in IE 10-.  */[type= "checkbox"],[type= "Radio"] {box-sizing:border-box; /* 1 */padding:0/* 2 */}/** * Correct the cursor style of increment and decrement buttons in Chrome. */[type= "number"]::-webkit-inner-spin-button,[type= "number"]::-webkit-outer-spin-button {Height:auto;} /** * 1. Correct the odd appEarance in Chrome and Safari. * 2. Correct the outline style in Safari.  */[type= "Search"] {-webkit-appearance:textfield; /* 1 */Outline-offset: -2px/* 2 */}/** * Remove the inner padding and cancel buttons in Chrome and Safari on MacOS. */[type= "Search"]::-webkit-search-cancel-button,[type= "search"]::-webkit-search-decoration {-webkit-appearance: none;} /** * 1. Correct the inability to style clickable types in IOS and Safari. * 2. Change font properties to ' inherit ' in Safari.  */::-webkit-file-upload-button {-webkit-appearance:button; /* 1 */font:inherit/* 2 */}/* Interactive ========================================================================= = *//* * Add The correct display in IE 9-. * 1. ADD the correct display in Edge, IE, and Firefox. */details,menu {display:block;} /* * ADD the correct display in all browsers. */summary {Display:list-item;} /* Scripting ========================================================================== *//** * Add the CorrecT display in IE 9-. */canvas {display:inline-block;} /** * Add The correct display in IE. */template {display:none;}  /* Hidden ========================================================================== *//** * Add the correct display in IE 10-. */[hidden] {display:none;}

　　

Normalize.css can initialize CSS, different browsers can unify the initial style