<b>, <i> vs <strong>, <em>
The b and strong tags by default make text bold. The i and em tags by default make text italicized.
Each browser has its own default styles, but result in similar appearances. Here is how they are styled in the popular browsers:
strong,
b {
font-weight: bold;
}
i,
cite,
em,
var,
address,
dfn {
font-style: italic;
}
b,
strong {
font-weight: bolder;
}
i,
cite,
em,
var,
dfn {
font-style: italic;
}
strong,
b {
font-weight: bold;
}
i,
cite,
em,
var,
address,
dfn {
font-style: italic;
}
Despite the fact that their appearances are similar, the strong and em tags add extra semantic meaning to the enclosed text, whereas b and i are purely visual.
According to the HTML 5 specifications, the
strong and
em tags indicate importance and emphasis respectively.
As far as accessibility goes, while a particular screen reading software may or may not pronounce it differently, using <strong> or <em> at least opens the possibility, whereas a screen reader will never pronounce text within <b> or <i> differently.