Why doesn’t the Tumblr blog show up when I search Tumblr

1. Go to the Customize section after you log in
2. Click on the Theme tab
3. Click Use custom HTML

This will bring up a edit box that contains the HTML and tumblr code used by the theme.

Put the code for the tags somewhere between the opening {block:Posts} and closing {/block:Posts} tags.

To start off easy, let's put the tags at the bottom of all your post types.

Where you see the following line:

{/block:Posts}

Insert the following starting chunk to look like this:

    {block:HasTags}
       {block:Tags}
          <a href="{TagURL}">{Tag}</a>
       {/block:Tags}
    {/block:HasTags}

{/block:Posts}

1. Click Update preview in the lower right corner of the edit box (or it will update itself)
2. Click Save + Close in the upper right of the dashboard.

Refresh your tumblr blog and you should now see the tags display.

You can read more of the specific tags markup needed on the Tags section of "Creating a custom HTML theme"

I'm fairly sure the only filtering you can do on posts (at least in the basic format, I know nothing of the API) is using tags. If the posts aren't tagged for author, then you probably can't. As noted here:

Tumblr has only two main types of page:

    PermalinkPage
    IndexPage

IndexPage include 3 sub-types:

    TagPage
    DayPage
    SearchPage

If what you want to filter for can't be achieved by these (and I'm fairly sure filtering using {PostAuthorURL}/{PostAuthorName} is not possible), then you can't do it with the base tumblr theme tools. If it's possible with Javascript and the API, I don,t have the competence to tell.