Say your image, image.png, is located in the images folder of your root directory, just put: <img src="/images/image.png" alt="image description"> If your site uses XHTML instead of HTML use: <img src="/images/image.png" alt="image description" />
Not really. Do it properly and shrink the image using a image tool such as Adobe Photoshop. Also the standards says you shouldn't use width and height in your img code.
my advice about images: - If you are using more cascaded images on the page they should have size definitions otherwise they wil be "jumping" when they load. Html will load first and then images which wont look nice. - When using photos and images with lots of colours try 60-75% Jpeg compression to keep nice crisp images. For additional parts of desing, like borders, edges and such try using Gif with selection of colour numbers. That will keep images realy small. - Always use DESCRIPTIVE alt tag and also use descriptive file name! This is good SEO Example: <img src="http://www.empire-elements.co.uk/projects_images/th/fresh-surf-wear-ecommerce-website.jpg" alt="FRESH! surf wear ecommerce website" width="200" height="189" />
You should use the alt tag to properly explain what kind of image it is. For example if it's a picture on a dog your alt tag should be: alt="Image of a dog". And not some tags for your site like: "dogs fact all about dogs etc". Your example alt tag doesnt say anything about the image that makes sense. And like I've said before: you should not use width and height.