<div class="welcometext">Welcome to LHA</div>
span class="welcometext">Welcome to LHA</
Divs are block-level elements
and will force a line break before and after unless you float them. Spans are inline elements
and behave differently. Note that widths and heights don't apply to inline elements, but you can control them somewhat by using line-height and padding.
On second thought, go with abduraooft's method. It's more semantically appropriate to use the header tags.