To help you get started you are missing a lot of end tags. For example, there are two places in your coding where you have an opening <center> tag, but never close it. You also start a <td> tag which is always within a <table> tag, but never put in/start a <table>...something like this will make a browser render your page in a very weird way.
Another thing to keep in mind is to always seperate your HTML coding from your CSS coding. In other words, put your HTML coding in one file and your CSS coding in another file. You will need to link your CSS file to your HTML file via the <link> tag and put in within your HTML files <head> tag.