The w3c organization gives style suggestions for html4_HTML/Xhtml_web page production

This is the style suggestion for HTML4 given by the w3c organization. Unfortunately, browsers have added their own private attributes, making the standard a cloud. But it is still of great reference significance to us.
Appendix D. Default style sheet for HTML 4
This appendix is ​​informative, not normative.

This style sheet describes the typical formatting of all HTML 4 ([HTML4]) elements based on extensive research into current UA practice. Developers are encouraged to use it as a default style sheet in their implementations.

The full presentation of some HTML elements cannot be expressed in CSS 2.1, including replaced elements ("img", "object "), scripting elements ("script", "applet"), form control elements, and frame elements.

For other elements, the legacy presentation can be described in CSS but the solution removes the element. For example , the FONT element can be replaced by attaching CSS declarations to other elements (e.g., DIV). Likewise, legacy presentation of presentational attributes (e.g., the "border" attribute on TABLE) can be described in CSS, but the markup in the source document must be changed.

<code class="css">html, address, <br>blockquote, <br>body, dd, div, <br>dl, dt, fieldset, form, <br>frame, frameset, <br>h1, h2, h3, h4, <br>h5, h6, noframes, <br>ol, p, ul, <span class="value"><font color="#0000ff">center</font></span>, <br>dir, hr, menu, <span class="value"><font color="#0000ff">pre</font></span>   { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">block</font></span> } <br>li              { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">list-item</font></span> } <br>head            { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">none</font></span> } <br>table           { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: table } <br>tr              { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">table-row</font></span> } <br>thead           { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">table-header-group</font></span> } <br>tbody           { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">table-row-group</font></span> } <br>tfoot           { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">table-footer-group</font></span> } <br>col             { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">table-column</font></span> } <br>colgroup        { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">table-column-group</font></span> } <br>td, th          { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">table-cell</font></span> } <br><span class="value"><font color="#0000ff">caption</font></span>         { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">table-caption</font></span> } <br>th              { <span class="attrib"><strong><font color="#000080">font-weight</font></strong></span>: <span class="value"><font color="#0000ff">bolder</font></span>; <span class="attrib"><strong><font color="#000080">text-align</font></strong></span>: <span class="value"><font color="#0000ff">center</font></span> } <br><span class="value"><font color="#0000ff">caption</font></span>         { <span class="attrib"><strong><font color="#000080">text-align</font></strong></span>: <span class="value"><font color="#0000ff">center</font></span> } <br>body            { <span class="attrib"><strong><font color="#000080">margin</font></strong></span>: <span class="number"><font color="#ff0000">8px</font></span> } <br>h1              { <span class="attrib"><strong><font color="#000080">font-size</font></strong></span>: <span class="number"><font color="#ff0000">2em</font></span>; <span class="attrib"><strong><font color="#000080">margin</font></strong></span>: .<span class="number"><font color="#ff0000">67em</font></span> <span class="number"><font color="#ff0000">0</font></span> } <br>h2              { <span class="attrib"><strong><font color="#000080">font-size</font></strong></span>: <span class="number"><font color="#ff0000">1.5em</font></span>; <span class="attrib"><strong><font color="#000080">margin</font></strong></span>: .<span class="number"><font color="#ff0000">75em</font></span> <span class="number"><font color="#ff0000">0</font></span> } <br>h3              { <span class="attrib"><strong><font color="#000080">font-size</font></strong></span>: <span class="number"><font color="#ff0000">1.17em</font></span>; <span class="attrib"><strong><font color="#000080">margin</font></strong></span>: .<span class="number"><font color="#ff0000">83em</font></span> <span class="number"><font color="#ff0000">0</font></span> } <br>h4, p, <br>blockquote, ul, <br>fieldset, form, <br>ol, dl, dir, <br>menu            { <span class="attrib"><strong><font color="#000080">margin</font></strong></span>: <span class="number"><font color="#ff0000">1.12em</font></span> <span class="number"><font color="#ff0000">0</font></span> } <br>h5              { <span class="attrib"><strong><font color="#000080">font-size</font></strong></span>: .<span class="number"><font color="#ff0000">83em</font></span>; <span class="attrib"><strong><font color="#000080">margin</font></strong></span>: <span class="number"><font color="#ff0000">1.5em</font></span> <span class="number"><font color="#ff0000">0</font></span> } <br>h6              { <span class="attrib"><strong><font color="#000080">font-size</font></strong></span>: .<span class="number"><font color="#ff0000">75em</font></span>; <span class="attrib"><strong><font color="#000080">margin</font></strong></span>: <span class="number"><font color="#ff0000">1.67em</font></span> <span class="number"><font color="#ff0000">0</font></span> } <br>h1, h2, h3, h4, <br>h5, h6, b, <br>strong          { <span class="attrib"><strong><font color="#000080">font-weight</font></strong></span>: <span class="value"><font color="#0000ff">bolder</font></span> } <br>blockquote      { <span class="attrib"><strong><font color="#000080">margin-left</font></strong></span>: <span class="number"><font color="#ff0000">40px</font></span>; <span class="attrib"><strong><font color="#000080">margin-right</font></strong></span>: <span class="number"><font color="#ff0000">40px</font></span> } <br>i, cite, em, <br>var, address    { <span class="attrib"><strong><font color="#000080">font-style</font></strong></span>: <span class="value"><font color="#0000ff">italic</font></span> } <br><span class="value"><font color="#0000ff">pre</font></span>, tt, <span class="value"><font color="#0000ff">code</font></span>, <br>kbd, samp       { <span class="attrib"><strong><font color="#000080">font-family</font></strong></span>: monospace } <br><span class="value"><font color="#0000ff">pre</font></span>             { <span class="attrib"><strong><font color="#000080">white-space</font></strong></span>: <span class="value"><font color="#0000ff">pre</font></span> } <br>button, textarea, <br>input, select   { <span class="attrib"><strong><font color="#000080">display</font></strong></span>: <span class="value"><font color="#0000ff">inline</font></span>-<span class="value"><font color="#0000ff">block</font></span> } <br>big             { <span class="attrib"><strong><font color="#000080">font-size</font></strong></span>: <span class="number"><font color="#ff0000">1.17em</font></span> } <br><span class="value"><font color="#0000ff">small</font></span>, <span class="value"><font color="#0000ff">sub</font></span>, sup { <span class="attrib"><strong><font color="#000080">font-size</font></strong></span>: .<span class="number"><font color="#ff0000">83em</font></span> } <br><span class="value"><font color="#0000ff">sub</font></span>             { <span class="attrib"><strong><font color="#000080">vertical-align</font></strong></span>: <span class="value"><font color="#0000ff">sub</font></span> } <br>sup             { <span class="attrib"><strong><font color="#000080">vertical-align</font></strong></span>: <span class="value"><font color="#0000ff">super</font></span> } <br>table           { <span class="attrib"><strong><font color="#000080">border-spacing</font></strong></span>: <span class="number"><font color="#ff0000">2px</font></span>; } <br>thead, tbody, <br>tfoot           { <span class="attrib"><strong><font color="#000080">vertical-align</font></strong></span>: <span class="value"><font color="#0000ff">middle</font></span> } <br>td, th, tr      { <span class="attrib"><strong><font color="#000080">vertical-align</font></strong></span>: inherit } <br>s, strike, del  { <span class="attrib"><strong><font color="#000080">text-decoration</font></strong></span>: <span class="value"><font color="#0000ff">line-through</font></span> } <br>hr              { <span class="attrib"><strong><font color="#000080">border</font></strong></span>: <span class="number"><font color="#ff0000">1px</font></span> <span class="value"><font color="#0000ff">inset</font></span> } <br>ol, ul, dir, <br>menu, dd        { <span class="attrib"><strong><font color="#000080">margin-left</font></strong></span>: <span class="number"><font color="#ff0000">40px</font></span> } <br>ol              { <span class="attrib"><strong><font color="#000080">list-style-type</font></strong></span>: <span class="value"><font color="#0000ff">decimal</font></span> } <br>ol ul, ul ol, <br>ul ul, ol ol    { <span class="attrib"><strong><font color="#000080">margin-top</font></strong></span>: <span class="number"><font color="#ff0000">0</font></span>; <span class="attrib"><strong><font color="#000080">margin-bottom</font></strong></span>: <span class="number"><font color="#ff0000">0</font></span> } <br>u, ins          { <span class="attrib"><strong><font color="#000080">text-decoration</font></strong></span>: <span class="value"><font color="#0000ff">underline</font></span> } <br>br:before       { <span class="attrib"><strong><font color="#000080">content</font></strong></span>: <span class="string"><font color="#008080">"\A"</font></span>; <span class="attrib"><strong><font color="#000080">white-space</font></strong></span>: <span class="value"><font color="#0000ff">pre</font></span>-line } <br><span class="value"><font color="#0000ff">center</font></span>          { <span class="attrib"><strong><font color="#000080">text-align</font></strong></span>: <span class="value"><font color="#0000ff">center</font></span> } <br>:link, :visited { <span class="attrib"><strong><font color="#000080">text-decoration</font></strong></span>: <span class="value"><font color="#0000ff">underline</font></span> } <br>:focus          { <span class="attrib"><strong><font color="#000080">outline</font></strong></span>: <span class="value"><font color="#0000ff">thin</font></span> <span class="value"><font color="#0000ff">dotted</font></span> <span class="value"><font color="#0000ff">invert</font></span> } <br> <br><span class="mlcom"><font color="#4040c2">/* Begin bidirectionality settings (do not change) */</font></span> <br>BDO[DIR=<span class="string"><font color="#008080">"ltr"</font></span>]  { <span class="attrib"><strong><font color="#000080">direction</font></strong></span>: <span class="value"><font color="#0000ff">ltr</font></span>; <span class="attrib"><strong><font color="#000080">unicode-bidi</font></strong></span>: <span class="value"><font color="#0000ff">bidi-override</font></span> } <br>BDO[DIR=<span class="string"><font color="#008080">"rtl"</font></span>]  { <span class="attrib"><strong><font color="#000080">direction</font></strong></span>: <span class="value"><font color="#0000ff">rtl</font></span>; <span class="attrib"><strong><font color="#000080">unicode-bidi</font></strong></span>: <span class="value"><font color="#0000ff">bidi-override</font></span> } <br> <br>*[DIR=<span class="string"><font color="#008080">"ltr"</font></span>]    { <span class="attrib"><strong><font color="#000080">direction</font></strong></span>: <span class="value"><font color="#0000ff">ltr</font></span>; <span class="attrib"><strong><font color="#000080">unicode-bidi</font></strong></span>: <span class="value"><font color="#0000ff">embed</font></span> } <br>*[DIR=<span class="string"><font color="#008080">"rtl"</font></span>]    { <span class="attrib"><strong><font color="#000080">direction</font></strong></span>: <span class="value"><font color="#0000ff">rtl</font></span>; <span class="attrib"><strong><font color="#000080">unicode-bidi</font></strong></span>: <span class="value"><font color="#0000ff">embed</font></span> } <br> <br>@media <span class="value"><font color="#0000ff">print</font></span> { <br>  h1            { <span class="attrib"><strong><font color="#000080">page-break-before</font></strong></span>: <span class="value"><font color="#0000ff">always</font></span> } <br>  h1, h2, h3, <br>  h4, h5, h6    { <span class="attrib"><strong><font color="#000080">page-break-after</font></strong></span>: <span class="value"><font color="#0000ff">avoid</font></span> } <br>  ul, ol, dl    { <span class="attrib"><strong><font color="#000080">page-break-before</font></strong></span>: <span class="value"><font color="#0000ff">avoid</font></span> } <br>}</code>

Appendix D. Default style sheet for HTML 4