[dabdinoor]

H1 tags do indeed influence your pagerank on certain search engines. Some factors that are ranked higher than H1 include the page title, page filename, and domain name. Meta tags are also a good place to put keywords, but they are less influential due to those who fill them with hundreds of innacurate keywords, having one or two keywords in your page filename and H1 tags is a good idea.

Now to answer your question, H1, and all other H tags have an implied line-break. To overcome this you simply need the following CSS rule:
h1 {
display: inline;
}

You may also be referring to the large Margin and Padding that surrounds H tags, varying by text size. To overcome those, use these rules:
h1 {
margin: 0;
padding:0;
}