reset csste strong tanımlanmamış olabilir.
ayrıca kullanmış olduğunuz font'ta buna sebebiyet olabilir. Eğer bold desteği yok ise.
@Mhmmd'nin dediği gibi css kodlarınızı paylaşabilirseniz daha iyi yardımcı olabiliriz.
Hocam anarschi den aldığım kodlar ile bir kaç yeri düzelttim

ancak bir kaç eksliklik var galiba buyrun
/* [url]http://meyerweb.com/eric/tools/css/reset/[/url]
v2.0 | 20110126
License: none (public domain)
*/
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, button, video {
margin: 0;
padding: 0;
border: 0;
font-size: 100%;
font: inherit;
vertical-align: baseline;
}
/* HTML5 display-role reset for older browsers */
article, aside, details, figcaption, figure,
footer, header, hgroup, menu, nav, section {
display: block;
}
body {
line-height: 1;
}
ol, ul {
list-style: none;
}
blockquote, q {
quotes: none;
}
blockquote:before, blockquote:after,
q:before, q:after {
content: '';
content: none;
}
table {
border-collapse: collapse;
border-spacing: 0;
}
a {text-decoration: none;}
:focus {outline: 0}
img.size-auto,
img.size-full,
img.size-large,
img.size-medium,
.attachment img {
max-width: 100%; /* When images are too wide for containing element, force them to fit. */
height: auto; /* Override height to match resized width for correct aspect ratio. */
}
.alignleft,
img.alignleft {
display: inline;
float: left;
margin-right: 14px;
margin-top: 4px;
}
.alignright,
img.alignright .noalignment img.noalignment{
display: inline;
float: right;
margin-left: 14px;
margin-top: 4px;
}
.aligncenter,
img.aligncenter {
clear: both;
display: block;
margin-left: auto;
margin-right: auto;
}
img.alignleft,
img.alignright,
img.aligncenter {
margin-bottom: 12px;
}
dl {
margin: 0 0 24px 0;
}
dt {
font-weight: bold;
}
dd {
margin-bottom: 18px;
}
strong {
font-weight: bold;
}
cite,
em,
i {
font-style: italic;
}
big {
font-size: 131.25%;
}
ins {
background: #ffc;
text-decoration: none;
}
blockquote {
font-style: italic;
padding: 0 10px 0 10px;
border-left-style: dashed;
border-left-width: 3px;
border-left-color: #CCCCCC;
margin-left: 10px;
font-size: 11px;
}
blockquote cite,
blockquote em,
blockquote i {
font-style: normal;
}
pre {
background: #f7f7f7;
color: #222;
line-height: 21px;
margin-bottom: 18px;
padding: 1.5em;
font-size: 12px;
}
abbr,
acronym {
border-bottom: 1px dotted #666;
cursor: help;
}
sup,
sub {
height: 0;
line-height: 1;
position: relative;
vertical-align: baseline;
}
sup {
bottom: 1ex;
}
sub {
top: .5ex;
}