Knowledgebase
How to change the header logo in Magento
Magento comes prepackaged with a default header logo. It's the Magento symbol with the text Magento next to it. You can change the logo with any image of your choice.
To do this first you need to upload the image. If the root Magento directory on your Magento hosting account is public_html, making the store accessible at yourdomain.com, then you need to upload the image in public_html/skin/frontend/default/default/images. You can do that from the Files section of the Pixie control panel, or you can use an FTP client (e.g. FileZilla).
After that log in to the admin panel of your Magento, go to System menu>Configuration, click on the Design button in the General menu on the left, and from the panels that are displayed on the right select Header. You'll see a field labeled Logo Image Src and it should be filled with images/logo.gif (the name of the default logo image is logo.gif). Just delete the part logo.gif and type the name of the image that you uploaded (e.g. new_logo.jpg). Then flush the Magento cache and the browser cache and refresh the frontend of your site. Keep in mind that Magento will not resize the logo and it will be displayed with the original dimensions of the uploaded image. So, if needed, you should crop and resize the image before you upload it on your account.
Keep in mind that when the image is uploaded in the images folder of the default theme (e.g. public_html/skin/frontend/default/default/images) it will also change the logo of other themes like modern, for example. However, if you upload the logo image in the folder only of the modern theme (e.g. public_html/skin/frontend/default/modern/images) and not in that of the default one, the new logo will be displayed only with the modern theme and not with the default one.
Another thing worth mentioning is that if you delete the original logo.gif image and you upload a new one with the same name, you don't have to change the default settings in the admin panel (provided you haven't already made changes to the Logo Image Src option).
The logo image displayed on the frontend is also a link to the homepage of the site. If you want to change the URL of that link, you can find how to do it in the article on changing the URL link of the header logo in Magento.