The page title is the key to quick orientation, so users immediately know if they’re on the page they want to be on. A clear title also helps users who’ve arrived to your site from a search and don’t know where they are in relation to the rest of the site.
Additionally, the first title is what the browser saves when the user bookmarks the page, so using just “Welcome to mysite.com” on every single page isn’t good enough. For the title in the head section, try something like “mysite.com: Top 10 Kids DVDs” or “mysite.com: Silk Ties Under Fifty Dollars.”
Google also relies heavily upon the browser bar title when its spider is crawling the web. Pages that use keywords appropriately will show up higher in search results. Use descriptive titles and you’ll stand out to users when they look at results from a Google search.