If your site is showing "Untitled Site" in your browser's tab, there is a way to change this.
1. Go to Page > Metadata.
2. In the "Page Title" field, enter your desired text.
3. Click OK to apply the changes.
4. Remember to save and republish your site in order for the amendments to appear online. The "Page Title" is also the area of your site that will become the title tag. The title tag is an important part of each page as it alerts search engines to the topic of a page.
Here is some more information on this if you would like to learn more: Adding Title, Description and Keywords Tags.