The text-transform property allows you to change the capitalization of text. Valid values are: uppercase, capitalize, lowercase, initial, inherit, and none

CSS:

.example1 {
    text-transform: uppercase;
}
.example2 {
    text-transform: capitalize;
}
.example3 {
    text-transform: lowercase;
}

HTML

<p class="example1">
    all letters in uppercase  <!-- "ALL LETTERS IN UPPERCASE" -->
</p>
<p class="example2">
    all letters in capitalize <!-- "All Letters In Capitalize (Sentence Case)" -->
</p>
<p class="example3">
    all letters in lowercase  <!-- "all letters in lowercase" -->
</p>