<div>Hello world！<nobr> Hello world!<nobr></div>

<div nowrap>Hello world! Hello world! Hello world! Hello world!</div>

div{
white-space:nowrap;
}

<div class="class1">hello </div>
<div class="class2">world! </div>
.class1 {float:left;}

<div class="class1">hello </div>
<div class="class2">world! </div>
.class1 {display:inline;}
.class2{display:inline;}