Edit HTML of Landing Page

For things that are hard-coded inside the editable areas of a Guided Landing Page template, unfortunately this is the only (non-API) way to go about it as far as I know.

For things that are hard-coded outside the editable areas of a Guided Landing Page (on the template) you can update this stuff at the template level.

I'd recommend while you're in there to use a relative path just to get in the habit of it -- so instead of replacing "http://" with "https://" you could instead just use "//".
Example: 

 could instead become:

That said, if I were tasked to do something like this, I might try and make life a little easier on myself by using a little CSS in the inspector to highlight things that needed to change so I didn't have to manually check every box all over the place.
You'll need to use the inspector console in your browser (Im using Chrome on a PC here) to add a bit of CSS to do the highlighting, but hopefully this can be a copy/paste/win tutorial that'll save ya a little time?

Here's what that might look like in the context of the Landing Page editor:

1) Open you Landing Page so that you're looking at the editable view of the page. 

2) Bring up the Dev Console by using F12 on a PC in Chrome or by right clicking an element in the canvas and choosing "Inspect Element". This should pop up the little bar at the bottom of the screen highlighted above. 

3) Click the highlighted tool (element picker) and that'll allow you to click on any element on the page to inspect it. I'd recommend clicking on any image you've got on the page, the header logo might be the easiest to use, but any image would do the trick here.

4) With the element selected, you'll want to click the "+" sign in the "Styles" panel off to the right. This will add a new "inspector-stylesheet" to your browser session that'll let you to inject some CSS into the page. This is usually used for testing new stuff out, but you can safely add stuff here without permanently changing anything on the page -- this is a temporary session-based stylesheet that'll go away as soon as you refresh the page. Clicking the "+" sign will populate a new style in the right panel that's got the "inspector-stylesheet" linked at the top right (highlighted green).
5) Click the "inspector-stylesheet" text link and that'll drive you into the "Sources" panel where you can add some CSS to this page.

6) Once you've click the "inspector-stylesheet" link, your console should look something like this -- you'll end up in the "Sources" tab and there will be some CSS there already from whatever you selected before you clicked the "+" button in the earlier step. Go ahead and erase anything that might be in there already so you've got an empty section here.

7) Add the CSS included below so that it ends up looking like the screenshot above. There are two pieces of CSS here -- the top bit is targeting any element with a src="" attribute that starts with "http:" -- this should catch all the images on the page and put a solid yellow outline around them. The second bit of CSS is targeted at any element with a href="" attribute that starts with "http:" -- this should catch links and buttons. Note - you might not need to update all the links/buttons if they point to an external source that is not your Marketo instance -- for example if they linked to your website and that also used http:// you'd want to leave that as-is. Basically you'd just want to change things that are hosted in Marketo from "http://" to "//".

Caption: Paste this code into the inspector console to draw outlines around images that have a src that starts with "http:" (yellow) and links that have a href that starts with "http:" (blue).

If this all comes together as expected, you should see any image or link that uses "http:" outlined in brightly colored boxes so you've got a queue to go have a look in a specific editable area to make changes there. You can repeat this process on other pages as you go.

Let me know if there's anything other than images and links/buttons that you find yourself needing to update and I'd be happy to try and update the CSS to catch those scenarios as well. Also happy to help out if you get stuck on any of the steps above, I'll keep an eye out for updates on this thread.

One way is to use the landing page APIs to get the content, sift through the response to get the content blocks with URLs to be replaced, and then update the respective content block with the updated HTML (essentially, rich text content). You could also use the approve LP endpoint to approve it programmatically as well. However, this process could easily consume a significant # of API calls if you have a large number of LPs to update.