Any ideas why <strong> tag doesn't work but CSS does?

<span class="bold">Some Title</span>

.bold
{
    font-weight:bold;
}

This renders boldly, however this:

<strong>Some Title</strong>

Does not. It just renders as regular text. I'm using the HTML5 doctype and the Google font:

<link href='http://fonts.googleapis.com/css?family=Droid+Sans&v2' rel='stylesheet' type='text/css'>

Anyone experienced this as well?

Edit: BoltClock suggested it might be CSS reset开发者_Go百科, here's the chunk for <strong>

/** CSS Reset **/
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed, 
figure, figcaption, footer, header, hgroup, 
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
    margin: 0;
    padding: 0;
    border: 0;
    font-size: 100%;
    font: inherit;
    vertical-align: baseline;
}

If there is nothing else for strong, then there's your problem (or rather, the CSS reset's problem).

The font: inherit style, together with all those selectors, is asking everything to inherit every font style from its parent. The default weight is, obviously, normal, so strong text is no longer bold until you redeclare it:

strong { font-weight: bold; }

(Some other obvious elements to reset styles for are b, em, i, code elements, quote elements, tables, headings, lists, etc.)

add:

strong{
 font-weight:bold;
}

to your CSS. Maybe somewhere you reset this tag.

Those resets are reseting not just padding and margins, as BoltClock explained, font:inherit can break your browsers deafault behaviour with displaying proper fonts style.

In addition to BoltClock's answer, I also found out that we must use the complete tag names for closing the tags, otherwise the STRONG tag used afterwards doesn't work. For example,

<H1> heading </H1>

instead of,

<H1> heading </>

For me the issue was Angular Material .mat-option class, for some reason using <b> or <strong> didn't work with their font. Changing their font to another one solved the issue for me.