Yes you can. For a summary of what meta data is and how it affects your website, see this artice from Search Engine Watch on meta data.
Here is a brief summary of how its used within your website:
Site Title Tag - Syntax: <title>Web Page Title</title>
An HTML tag within the Head tag is used to define the title of a Web page. The content of the Title tag is displayed by browsers on the Title bar located at the top of the browser window. Search engines use the Title tag to provide a link to the site matching the user's query. The text in the Title tag is one of the most important factors influencing search engine ranking algorithms. By populating your most important keywords in the Title tag, you dramatically increase the search engine ranking of the page for those keywords.
In Joomla: The site title tag is set globally and was done when your website was created. If you feel you want to change this, please contact us and we can discuss this with you further. Individual page titles are derived from the page
name so for example, if the page name is called Home, the page title
will also have home in it.
Site Description - Syntax: <meta name="Description" content=">
This is a Meta tag that provides a brief description of a Web page. It is important the description clearly describes the purpose of the page. The importance of the Description tag as an element of the ranking algorithm has decreased significantly over years, but there are still search engines that support this tag. They log descriptions of the indexed pages and often display them with the Title in their results.
The length of a displayed description varies per search engine. Therefore you should place the most important keywords at the beginning of the first sentence -- this will guarantee that both users and search engines will see the most important information about your site.
In Joomla: The site description is set globally and was done when your website was created. If you feel you want to change this, please contact us and we can discuss this with you further.
Individual pages can have their own description. In order to define this, select the meta info tab on the right hand side when editing the page. There is a Description section where you can add your own. Please note that this is a description about this page and not the website in general.
Site Keywords - Syntax: < META name="Keywords" content="keyword1, keyword2, keyword3">
This is Meta tag that lists the words or phrases about the contents of the Web page. This tag provides some additional text for crawler-based search engines. However because of frequent attempts to abuse their system, most search engines ignore this tag. Please note that none of the major crawler-based search engines except Inktomi provide support for the Keywords Meta tag.
Similar to the description tag, there is a limit in the number of captured characters in Keywords meta tag. Ensure you've chosen keywords that are relevant to the content of your site. Avoid repetitions as search engines can penalize your rankings. Move the most important keywords to the beginning to increase their prominence.
In Joomla: The site title keywords may have been set globally and
was done when your website was created. If you feel you want to change these, please contact us and we can discuss this with you further.
Individual pages can have their own set of keywords appropriate to that page. In order to define these, select the meta info tab on the right hand side when editing the page. There is a keywords section where you can add your own - please separate all keywords by a comma e.g. bike,bikes,bicycles etc
Site Heading Tags - Syntax: <H1> <H2> <H3>
Your page either has no <h1 h2 or h3> headings, or has no text in the first heading on the page! It is crucial that your keyword appears in one of these headings. We also recommend that you put an <h1 h2 and h3> heading as close to the beginning of your page as possible. Search engines traditionally consider text in the headings to be essential, and having your keyword there will positively influence your website's overall optimality.
In Joomla: We have defined styles for H1, H2 and H3 tags and you can use these by selecting appropriate heading from the first drop down box in the content editor. By default, it will say 'Normal' but you can select any of the options if you want to.