vertical-align

A propriedade  vertical-align do CSS especifica o alinhamento vertical de um inline ou caixa table-cell.

/* keyword values */
vertical-align: baseline;
vertical-align: sub;
vertical-align: super;
vertical-align: text-top;
vertical-align: text-bottom;
vertical-align: middle;
vertical-align: top;
vertical-align: bottom;

/* <length> values */
vertical-align: 10em;
vertical-align: 4px;

/* <percentage> values */
vertical-align: 20%;

/* Global values */
vertical-align: inherit;
vertical-align: initial;
vertical-align: unset;

A propriedade vertical-align pode ser usada em dois contextos:

• Para alinhar verticalmente uma caixa de elementos inline dentro  dentro de sua caixa de linha. Por exemplo, poderia ser usado para alinhar verticalmente um  <img> em uma linha de texto:

<p>
top:<img style="vertical-align:top" src="https://mdn.mozillademos.org/files/15189/star.png"/>
middle:<img style="vertical-align:middle" src="https://mdn.mozillademos.org/files/15189/star.png"/>
bottom:<img style="vertical-align:bottom" src="https://mdn.mozillademos.org/files/15189/star.png"/>
super:<img style="vertical-align:super" src="https://mdn.mozillademos.org/files/15189/star.png"/>
sub:<img style="vertical-align:sub" src="https://mdn.mozillademos.org/files/15189/star.png"/>
</p>
<p>
text-top:<img style="vertical-align:text-top" src="https://mdn.mozillademos.org/files/15189/star.png"/>
text-bottom:<img  style="vertical-align:text-bottom" src="https://mdn.mozillademos.org/files/15189/star.png"/>
0.2em:<img style="vertical-align:0.2em" src="https://mdn.mozillademos.org/files/15189/star.png"/>
-1em:<img  style="vertical-align:-1em" src="https://mdn.mozillademos.org/files/15189/star.png"/>
20%:<img style="vertical-align:20%" src="https://mdn.mozillademos.org/files/15189/star.png"/>
-100%:<img  style="vertical-align:-100%" src="https://mdn.mozillademos.org/files/15189/star.png"/>
</p>

#* {
  box-sizing: border-box;
}

img {
  margin-right: 0.5em;
}

p {
  height: 3em;
  padding: 0 .5em;
  font-family: monospace;
  text-decoration: underline overline;
  margin-left: auto;
  margin-right: auto;
  width: 80%;
}

• Para alinhar verticalmente o conteudo de uma celula em uma tabela:

<table>
  <tr>
    <td style="vertical-align: baseline">baseline</td>
    <td style="vertical-align: top">top</td>
    <td style="vertical-align: middle">middle</td>
    <td style="vertical-align: bottom">bottom</td>
    <td>
      <p>There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.</p>
<p>There is another theory which states that this has already happened.</p>
    </td>
  </tr>
</table>

table {
  margin-left: auto;
  margin-right: auto;
  width: 80%;
}

table, th, td {
  border: 1px solid black;
}

td {
  padding: 0.5em;
  font-family: monospace;
}

Observe que  vertical-align é aplicado apenas em elementos inline e table-cell: Você não pode usar isso para alinhar verticalmente elementos de nível de bloco.

This property is specified as one of the keyword values listed below.

Most of the values vertically align the element relative to its parent element:
Essas propriedades alinham verticalmente o elemento relativamente a seu elemento pai

baseline

Aligns the baseline of the element with the baseline of its parent. The baseline of some replaced elements, like <textarea>, is not specified by the HTML specification, meaning that their behavior with this keyword may change from one browser to the other.

sub

Aligns the baseline of the element with the subscript-baseline of its parent.

super

Aligns the baseline of the element with the superscript-baseline of its parent.

text-top

Aligns the top of the element with the top of the parent element's font.

text-bottom

Aligns the bottom of the element with the bottom of the parent element's font.

middle

Aligns the middle of the element with the baseline plus half the x-height of the parent.

<length> (en-US)

Aligns the baseline of the element at the given length above the baseline of its parent.

<percentage> (en-US)

Like <length> values, with the percentage being a percent of the line-height (en-US) property.

(Negative values are allowed for <length> and <percentage>.)

The following two values vertically align the element relative to the entire line rather than relative to its parent:

top

Align the top of the element and its descendants with the top of the entire line.

bottom

Align the bottom of the element and its descendants with the bottom of the entire line.

For elements that do not have a baseline, the bottom margin edge is used instead.

baseline (and sub, super, text-top, text-bottom, <length>, and <percentage>)

Align the baseline of the cell with the baseline of all other cells in the row that are baseline-aligned.

top

Align the top padding edge of the cell with the top of the row.

middle

Center the padding box of the cell within the row.

bottom

Align the bottom padding edge of the cell with the bottom of the row.

Negative values are allowed.

baseline | (en-US) sub | (en-US) super | (en-US) text-top | (en-US) text-bottom | (en-US) middle | (en-US) top | (en-US) bottom | (en-US) <percentage> (en-US) | (en-US) <length> (en-US)

• line-height (en-US), text-align, margin
• Understanding vertical-align, or "How (Not) To Vertically Center Content"
• All You Need To Know About Vertical-Align