It is the page of a website where user sees it first before proceeding to the original content of that site. Users will get an option like continue and when you click on that you will be redirected to original content of that site. Some of the splash pages doesn't have to continue and they will automatically redirect to the website main content.
These splash pages are used for promotions, advertisements, services and products of a company. So, that the user gets a clear view about the website. Splash page also contains animations, graphics and sounds.
In Salesforce, splash page appears whenever a tab with a custom object, which consists of custom link(splash page) is clicked. This custom link is displayed as splash page. We will provide the custom link(URL or any other reference) at the time of creation of a custom link.
How to Create Custom Link:
Click on Setup --> Build --> Customize --> Home --> Custom link.
Click on the new custom link. In the custom link edit, fill the details like name, description, protected component, etc. You can select the behavior based on your requirement by viewing the behavior options.
Select the content source like URL, Visualforce page or Custom S-Control based upon the source you have. You can also provide a formula with functions so that it works according to it. Click on save.
Assigning custom link to tab:
Click Setup --> Build --> Create --> Tabs.
Create a new tab or modify existing tab. After creating or editing the tab, it has an object, label and style. After that you will find, choose a Home Page Custom Link to show as a splash page when the first time your users click on this tab.
Select the custom link which you already created and click on save. Next when you click on the tab created, splash page is displayed. This splash page contains two options don't show again and continue. Upon clicking any of the options, you can use the tab.
If you want to add an image or video to splash page instead of URL, you can do it by adding static resource, which stores the image or video you want to display.
How to Create Static Resource:
Click on Setup --> Build --> Develop --> Static Resources.
Click on new and select the name, file(image or video file), cache control and save it.
On the detail page of a static resource, right click on view file and copy address.
Creation of Custom Link to display Image or Video:
Now go to the custom link splash page and create a custom link with the copied address above and assign it to the tab.
Therefore, whenever the tab is opened, image or video is displayed which you provided.
When you create a link to static image or video, there is a time stamp included in the link which is not needed to display the output.
A custom link label can't exceed 1024 characters. A link URL can be up to 2,048 bytes. When data is substituted for the tokens in the URL, the link can exceed 3,000 bytes. Some browsers enforce limits to the maximum URL length.